/ Code Analysis

Linters Runner for Go 5x faster than gometalinter

Linters Runner for Go 5x faster than gometalinter

GolangCI-Lint

GolangCI-Lint is a linters aggregator. It's fast: on average 5 times faster than gometalinter. It's easy to integrate and use, has nice output and has a minimum number of false positives. It supports go modules.

GolangCI-Lint has integrations with VS Code, GNU Emacs, Sublime Text.

Sponsored by GolangCI.com: SaaS service for running linters on Github pull requests. Free for Open Source.

GolangCI-Lintv

GolangCI-Lint

Install

CI Installation

Most installations are done for CI (travis, circleci etc). It's important to have reproducible CI:
don't start to fail all builds at the same time. With golangci-lint this can happen if you
use --enable-all and a new linter is added or even without --enable-all: when one upstream linter is upgraded.

It's highly recommended to install a fixed version of golangci-lint.
Releases are available on the releases page.

Latest version: GitHub release

Here is the recommended way to install golangci-lint (replace vX.Y.Z with the latest version):

# binary will be $(go env GOPATH)/bin/golangci-lint
curl -sfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh| sh -s -- -b $(go env GOPATH)/bin vX.Y.Z

# or install it into ./bin/
curl -sfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh| sh -s vX.Y.Z

# In alpine linux (as it does not come with curl by default)
wget -O - -q https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh| sh -s vX.Y.Z

golangci-lint --version

Periodically update version of golangci-lint: the project is under active development
and is constantly being improved. But please always check for newly found issues and
update if needed.

Local Installation

Local installation is not recommended for your CI pipeline. Only install the linter this way in a local development environment.

Windows, MacOS and Linux

go get -u github.com/golangci/golangci-lint/cmd/golangci-lint

With go1.12 or later you can get a particular version

GO111MODULE=on go get github.com/golangci/golangci-lint/cmd/[email protected]

MacOS

You can also install it on MacOS using brew:

brew install golangci/tap/golangci-lint
brew upgrade golangci/tap/golangci-lint

--version

If you need your local golangci-lint --version to show proper version additionally run:

cd $(go env GOPATH)/src/github.com/golangci/golangci-lint/cmd/golangci-lint
go install -ldflags "-X 'main.version=$(git describe --tags)' -X 'main.commit=$(git rev-parse --short HEAD)' -X 'main.date=$(date)'"

On Windows, you can run the above commands with Git Bash, which comes with Git for Windows.

Trusted By

The following companies/products use golangci-lint:

The following great projects use golangci-lint:

Quick Start

To run golangci-lint execute:

golangci-lint run

It's an equivalent of executing:

golangci-lint run ./...

You can choose which directories and files to analyze:

golangci-lint run dir1 dir2/... dir3/file1.go

Directories are NOT analyzed recursively. To analyze them recursively append /... to their path.

GolangCI-Lint can be used with zero configuration. By default the following linters are enabled:

$ golangci-lint help linters
Enabled by default linters:
deadcode: Finds unused code [fast: true, auto-fix: false]
errcheck: Errcheck is a program for checking for unchecked errors in go programs. These unchecked errors can be critical bugs in some cases [fast: true, auto-fix: false]
gosimple: Linter for Go source code that specializes in simplifying a code [fast: false, auto-fix: false]
govet (vet, vetshadow): Vet examines Go source code and reports suspicious constructs, such as Printf calls whose arguments do not align with the format string [fast: false, auto-fix: false]
ineffassign: Detects when assignments to existing variables are not used [fast: true, auto-fix: false]
staticcheck: Staticcheck is a go vet on steroids, applying a ton of static analysis checks [fast: false, auto-fix: false]
structcheck: Finds unused struct fields [fast: true, auto-fix: false]
typecheck: Like the front-end of a Go compiler, parses and type-checks Go code [fast: true, auto-fix: false]
unused: Checks Go code for unused constants, variables, functions and types [fast: false, auto-fix: false]
varcheck: Finds unused global variables and constants [fast: true, auto-fix: false]

and the following linters are disabled by default:

$ golangci-lint help linters
...
Disabled by default linters:
bodyclose: checks whether HTTP response body is closed successfully [fast: false, auto-fix: false]
depguard: Go linter that checks if package imports are in a list of acceptable packages [fast: true, auto-fix: false]
dogsled: Checks assignments with too many blank identifiers (e.g. x, _, _, _, := f()) [fast: true, auto-fix: false]
dupl: Tool for code clone detection [fast: true, auto-fix: false]
funlen: Tool for detection of long functions [fast: true, auto-fix: false]
gochecknoglobals: Checks that no globals are present in Go code [fast: true, auto-fix: false]
gochecknoinits: Checks that no init functions are present in Go code [fast: true, auto-fix: false]
goconst: Finds repeated strings that could be replaced by a constant [fast: true, auto-fix: false]
gocritic: The most opinionated Go source code linter [fast: true, auto-fix: false]
gocyclo: Computes and checks the cyclomatic complexity of functions [fast: true, auto-fix: false]
godox: Tool for detection of FIXME, TODO and other comment keywords [fast: true, auto-fix: false]
gofmt: Gofmt checks whether code was gofmt-ed. By default this tool runs with -s option to check for code simplification [fast: true, auto-fix: true]
goimports: Goimports does everything that gofmt does. Additionally it checks unused imports [fast: true, auto-fix: true]
golint: Golint differs from gofmt. Gofmt reformats Go source code, whereas golint prints out style mistakes [fast: true, auto-fix: false]
gosec (gas): Inspects source code for security problems [fast: true, auto-fix: false]
interfacer: Linter that suggests narrower interface types [fast: false, auto-fix: false]
lll: Reports long lines [fast: true, auto-fix: false]
maligned: Tool to detect Go structs that would take less memory if their fields were sorted [fast: true, auto-fix: false]
misspell: Finds commonly misspelled English words in comments [fast: true, auto-fix: true]
nakedret: Finds naked returns in functions greater than a specified function length [fast: true, auto-fix: false]
prealloc: Finds slice declarations that could potentially be preallocated [fast: true, auto-fix: false]
scopelint: Scopelint checks for unpinned variables in go programs [fast: true, auto-fix: false]
stylecheck: Stylecheck is a replacement for golint [fast: false, auto-fix: false]
unconvert: Remove unnecessary type conversions [fast: true, auto-fix: false]
unparam: Reports unused function parameters [fast: false, auto-fix: false]
whitespace: Tool for detection of leading and trailing whitespace [fast: true, auto-fix: true]

Pass -E/--enable to enable linter and -D/--disable to disable:

golangci-lint run --disable-all -E errcheck

Editor Integration

  1. Go for Visual Studio Code.
    Recommended settings for VS Code are:

    "go.lintTool":"golangci-lint",
    "go.lintFlags": [
      "--fast"
    ]
    

    Using it in an editor without --fast can freeze your editor.
    Golangci-lint automatically discovers .golangci.yml config for edited file: you don't need to configure it in VS Code settings.

  2. Sublime Text - plugin for SublimeLinter.

  3. GoLand

    • Configure File Watcher with arguments run --print-issued-lines=false $FileDir$.
    • Predefined File Watcher will be added in issue.
  4. GNU Emacs

  5. Vim

  6. Atom - go-plus supports golangci-lint.

Shell Completion

golangci-lint can generate bash completion file.

Mac OS X

Yhere are two versions of bash-completion, v1 and v2. V1 is for Bash 3.2 (which is the default on macOS), and v2 is for Bash 4.1+. The golangci-lint completion script doesn’t work correctly with bash-completion v1 and Bash 3.2. It requires bash-completion v2 and Bash 4.1+. Thus, to be able to correctly use golangci-lint completion on macOS, you have to install and use Bash 4.1+ (instructions). The following instructions assume that you use Bash 4.1+ (that is, any Bash version of 4.1 or newer).

Install bash-completion v2:

brew install [email protected]
echo 'export BASH_COMPLETION_COMPAT_DIR="/usr/local/etc/bash_completion.d"' >>~/.bashrc
echo '[[ -r "/usr/local/etc/profile.d/bash_completion.sh" ]] && . "/usr/local/etc/profile.d/bash_completion.sh"' >>~/.bashrc
exec bash # reload and replace (if it was updated) shell
type _init_completion && echo "completion is OK" # verify that bash-completion v2 is correctly installed

Add golangci-lint bash completion:

echo 'source <(golangci-lint completion bash)' >>~/.bashrc
source ~/.bashrc

Linux

See kubectl instructions and don't forget to replace kubectl with golangci-lint.

Comparison

golangci-lint vs gometalinter

GolangCI-Lint was created to fix the following issues with gometalinter:

  1. Slow work: gometalinter usually works for minutes in average projects.
    GolangCI-Lint works 2-7x times faster by reusing work.
  2. Huge memory consumption: parallel linters don't share the same program representation and can consume
    n times more memory (n - concurrency). GolangCI-Lint fixes it by sharing representation and consumes 26% less memory.
  3. Doesn't use real bounded concurrency: if you set it to n it can take up to n*n threads because of
    forced threads in specific linters. gometalinter can't do anything about it because it runs linters as
    black boxes in forked processes. In GolangCI-Lint we run all linters in one process and completely control
    them. Configured concurrency will be correctly bounded.
    This issue is important because you often want to set concurrency to the CPUs count minus one to
    ensure you do not freeze your PC and be able to work on it while analyzing code.
  4. Lack of nice output. We like how the gcc and clang compilers format their warnings: using colors,
    printing warning lines and showing the position in line
    .
  5. Too many issues. GolangCI-Lint cuts a lot of issues by using default exclude list of common false-positives.
    By default, it has enabled smart issues processing: merge multiple issues for one line, merge issues with the
    same text or from the same linter. All of these smart processors can be configured by the user.
  6. Integration into large codebases. A good way to start using linters in a large project is not to fix a plethora
    of existing issues, but to set up CI and fix only issues in new commits. You can use revgrep for it, but it's
    yet another utility to install and configure. With golangci-lint it's much easier: revgrep is already built into
    golangci-lint and you can use it with one option (-n, --new or --new-from-rev).
  7. Installation. With gometalinter, you need to run a linters installation step. It's easy to forget this step and
    end up with stale linters. It also complicates CI setup. GolangCI-Lint requires no installation of linters.
  8. Yaml or toml config. Gometalinter's JSON isn't convenient for config files.

golangci-lint vs Running Linters Manually

  1. It will be much slower because golangci-lint runs all linters in parallel and shares 50-80% of linters work.
  2. It will have less control and more false-positives: some linters can't be properly configured without hacks.
  3. It will take more time because of different usages and need of tracking of versions of n linters.

Performance

Benchmarks were executed on MacBook Pro (Retina, 13-inch, Late 2013), 2,4 GHz Intel Core i5, 8 GB 1600 MHz DDR3.
It has 4 cores and concurrent linting as a default consuming all cores.
Benchmark was run (and measured) automatically, see the code
here (BenchmarkWithGometalinter).

We measure peak memory usage (RSS) by tracking of processes RSS every 5 ms.

Comparison with gometalinter

We compare golangci-lint and gometalinter in default mode, but explicitly enable all linters because of small differences in the default configuration.

$ golangci-lint run --no-config --issues-exit-code=0 --deadline=30m \
  --disable-all --enable=deadcode  --enable=gocyclo --enable=golint --enable=varcheck \
  --enable=structcheck --enable=maligned --enable=errcheck --enable=dupl --enable=ineffassign \
  --enable=interfacer --enable=unconvert --enable=goconst --enable=gosec --enable=megacheck
$ gometalinter --deadline=30m --vendor --cyclo-over=30 --dupl-threshold=150 \
  --exclude=<default golangci-lint excludes> --skip=testdata --skip=builtin \
  --disable-all --enable=deadcode  --enable=gocyclo --enable=golint --enable=varcheck \
  --enable=structcheck --enable=maligned --enable=errcheck --enable=dupl --enable=ineffassign \
  --enable=interfacer --enable=unconvert --enable=goconst --enable=gosec --enable=megacheck
  ./...
Repository GolangCI Time GolangCI Is Faster than Gometalinter GolangCI Memory GolangCI eats less memory than Gometalinter
gometalinter repo, 4 kLoC 6s 6.4x 0.7GB 33%
self-repo, 4 kLoC 12s 7.5x 1.2GB 41%
beego, 50 kLoC 10s 4.2x 1.4GB 9%
hugo, 70 kLoC 15s 6.1x 1.6GB 44%
consul, 127 kLoC 58s 4x 2.7GB 41%
terraform, 190 kLoC 2m13s 1.6x 4.8GB 0%
go-ethereum, 250 kLoC 33s 5x 3.6GB 0%
go source ($GOROOT/src), 1300 kLoC 2m45s 2x 4.7GB 0%

On average golangci-lint is 4.6 times faster than gometalinter. Maximum difference is in the
self-repo: 7.5 times faster, minimum difference is in terraform source code repo: 1.8 times faster.

On average golangci-lint consumes 26% less memory.

Why golangci-lint is faster

Golangci-lint directly calls linters (no forking) and reuses 80% of work by parsing program only once.
Read this section for details.

Memory Usage of Golangci-lint

A trade-off between memory usage and execution time can be controlled by GOGC environment variable.
Less GOGC values trigger garbage collection more frequently and golangci-lint consumes less memory and more CPU. Below is the trade-off table for running on this repo:

GOGC Peak Memory, GB Executon Time, s
5 1.1 60
10 1.1 34
20 1.3 25
30 1.6 20.2
50 2.0 17.1
80 2.2 14.1
100 (default) 2.2 13.8
off 3.2 9.3

Internals

  1. Work sharing
    The key difference with gometalinter is that golangci-lint shares work between specific linters (golint, govet, ...).
    We don't fork to call specific linter but use its API.
    For small and medium projects 50-90% of work between linters can be reused.

    • load []*packages.Package by go/packages once

      We load program (parsing all files and type-checking) only once for all linters. For the most of linters
      it's the most heavy operation: it takes 5 seconds on 8 kLoC repo and 11 seconds on $GOROOT/src.

    • build ssa.Program once

      Some linters (megacheck, interfacer, unparam) work on SSA representation.
      Building of this representation takes 1.5 seconds on 8 kLoC repo and 6 seconds on $GOROOT/src.

    • parse source code and build AST once

      Parsing one source file takes 200 us on average. Parsing of all files in $GOROOT/src takes 2 seconds.
      Currently we parse each file more than once because it's not the bottleneck. But we already save a lot of
      extra parsing. We're planning to parse each file only once.

    • walk files and directories once

      It takes 300-1000 ms for $GOROOT/src.

  2. Smart linters scheduling

    We schedule linters by a special algorithm which takes estimated execution time into account. It allows
    to save 10-30% of time when one of heavy linters (megacheck etc) is enabled.

  3. Don't fork to run shell commands

All linters are vendored in the /vendor folder: their version is fixed, they are builtin
and you don't need to install them separately.

Supported Linters

To see a list of supported linters and which linters are enabled/disabled:

golangci-lint help linters

Enabled By Default Linters

  • govet - Vet examines Go source code and reports suspicious constructs, such as Printf calls whose arguments do not align with the format string
  • errcheck - Errcheck is a program for checking for unchecked errors in go programs. These unchecked errors can be critical bugs in some cases
  • staticcheck - Staticcheck is a go vet on steroids, applying a ton of static analysis checks
  • unused - Checks Go code for unused constants, variables, functions and types
  • gosimple - Linter for Go source code that specializes in simplifying a code
  • structcheck - Finds unused struct fields
  • varcheck - Finds unused global variables and constants
  • ineffassign - Detects when assignments to existing variables are not used
  • deadcode - Finds unused code
  • typecheck - Like the front-end of a Go compiler, parses and type-checks Go code

Disabled By Default Linters (-E/--enable)

  • bodyclose - checks whether HTTP response body is closed successfully
  • golint - Golint differs from gofmt. Gofmt reformats Go source code, whereas golint prints out style mistakes
  • stylecheck - Stylecheck is a replacement for golint
  • gosec - Inspects source code for security problems
  • interfacer - Linter that suggests narrower interface types
  • unconvert - Remove unnecessary type conversions
  • dupl - Tool for code clone detection
  • goconst - Finds repeated strings that could be replaced by a constant
  • gocyclo - Computes and checks the cyclomatic complexity of functions
  • gofmt - Gofmt checks whether code was gofmt-ed. By default this tool runs with -s option to check for code simplification
  • goimports - Goimports does everything that gofmt does. Additionally it checks unused imports
  • maligned - Tool to detect Go structs that would take less memory if their fields were sorted
  • depguard - Go linter that checks if package imports are in a list of acceptable packages
  • misspell - Finds commonly misspelled English words in comments
  • lll - Reports long lines
  • unparam - Reports unused function parameters
  • dogsled - Checks assignments with too many blank identifiers (e.g. x, _, _, _, := f())
  • nakedret - Finds naked returns in functions greater than a specified function length
  • prealloc - Finds slice declarations that could potentially be preallocated
  • scopelint - Scopelint checks for unpinned variables in go programs
  • gocritic - The most opinionated Go source code linter
  • gochecknoinits - Checks that no init functions are present in Go code
  • gochecknoglobals - Checks that no globals are present in Go code
  • godox - Tool for detection of FIXME, TODO and other comment keywords
  • funlen - Tool for detection of long functions
  • whitespace - Tool for detection of leading and trailing whitespace

Configuration

The config file has lower priority than command-line options. If the same bool/string/int option is provided on the command-line
and in the config file, the option from command-line will be used.
Slice options (e.g. list of enabled/disabled linters) are combined from the command-line and config file.

To see a list of enabled by your configuration linters:

golangci-lint linters

Command-Line Options

golangci-lint run -h
Usage:
  golangci-lint run [flags]

Flags:
      --out-format string           Format of output: colored-line-number|line-number|json|tab|checkstyle|code-climate|junit-xml (default "colored-line-number")
      --print-issued-lines          Print lines of code with issue (default true)
      --print-linter-name           Print linter name in issue line (default true)
      --issues-exit-code int        Exit code when issues were found (default 1)
      --build-tags strings          Build tags
      --deadline duration           Deadline for total work (default 1m0s)
      --tests                       Analyze tests (*_test.go) (default true)
      --print-resources-usage       Print avg and max memory usage of golangci-lint and total time
  -c, --config PATH                 Read config from file path PATH
      --no-config                   Don't read config
      --skip-dirs strings           Regexps of directories to skip
      --skip-dirs-use-default       Use or not use default excluded directories:
                                      - (^|/)vendor($|/)
                                      - (^|/)third_party($|/)
                                      - (^|/)testdata($|/)
                                      - (^|/)examples($|/)
                                      - (^|/)Godeps($|/)
                                      - (^|/)builtin($|/)
                                     (default true)
      --skip-files strings          Regexps of files to skip
  -E, --enable strings              Enable specific linter
  -D, --disable strings             Disable specific linter
      --enable-all                  Enable all linters
      --disable-all                 Disable all linters
  -p, --presets strings             Enable presets (bugs|complexity|format|performance|style|unused) of linters. Run 'golangci-lint linters' to see them. This option implies option --disable-all
      --fast                        Run only fast linters from enabled linters set (first run won't be fast)
  -e, --exclude strings             Exclude issue by regexp
      --exclude-use-default         Use or not use default excludes:
                                      # errcheck: Almost all programs ignore errors on these functions and in most cases it's ok
                                      - Error return value of .((os\.)?std(out|err)\..*|.*Close|.*Flush|os\.Remove(All)?|.*printf?|os\.(Un)?Setenv). is not checked
                                    
                                      # golint: Annoying issue about not having a comment. The rare codebase has such comments
                                      - (comment on exported (method|function|type|const)|should have( a package)? comment|comment should be of the form)
                                    
                                      # golint: False positive when tests are defined in package 'test'
                                      - func name will be used as test\.Test.* by other packages, and that stutters; consider calling this
                                    
                                      # govet: Common false positives
                                      - (possible misuse of unsafe.Pointer|should have signature)
                                    
                                      # staticcheck: Developers tend to write in C-style with an explicit 'break' in a 'switch', so it's ok to ignore
                                      - ineffective break statement. Did you mean to break out of the outer loop
                                    
                                      # gosec: Too many false-positives on 'unsafe' usage
                                      - Use of unsafe calls should be audited
                                    
                                      # gosec: Too many false-positives for parametrized shell calls
                                      - Subprocess launch(ed with variable|ing should be audited)
                                    
                                      # gosec: Duplicated errcheck checks
                                      - G104
                                    
                                      # gosec: Too many issues in popular repos
                                      - (Expect directory permissions to be 0750 or less|Expect file permissions to be 0600 or less)
                                    
                                      # gosec: False positive is triggered by 'src, err := ioutil.ReadFile(filename)'
                                      - Potential file inclusion via variable
                                     (default true)
      --max-issues-per-linter int   Maximum issues count per one linter. Set to 0 to disable (default 50)
      --max-same-issues int         Maximum count of issues with the same text. Set to 0 to disable (default 3)
  -n, --new                         Show only new issues: if there are unstaged changes or untracked files, only those changes are analyzed, else only changes in HEAD~ are analyzed.
                                    It's a super-useful option for integration of golangci-lint into existing large codebase.
                                    It's not practical to fix all existing issues at the moment of integration: much better to not allow issues in new code.
                                    For CI setups, prefer --new-from-rev=HEAD~, as --new can skip linting the current patch if any scripts generate unstaged files before golangci-lint runs.
      --new-from-rev REV            Show only new issues created after git revision REV
      --new-from-patch PATH         Show only new issues created in git patch with file path PATH
      --fix                         Fix found issues (if it's supported by the linter)
  -h, --help                        help for run

Global Flags:
      --color string              Use color when printing; can be 'always', 'auto', or 'never' (default "auto")
  -j, --concurrency int           Concurrency (default NumCPU) (default 8)
      --cpu-profile-path string   Path to CPU profile output file
      --mem-profile-path string   Path to memory profile output file
      --trace-path string         Path to trace output file
  -v, --verbose                   verbose output

Config File

GolangCI-Lint looks for config files in the following paths from the current working directory:

  • .golangci.yml
  • .golangci.toml
  • .golangci.json

GolangCI-Lint also searches for config files in all directories from the directory of the first analyzed path up to the root.
To see which config file is being used and where it was sourced from run golangci-lint with -v option.

Config options inside the file are identical to command-line options.
You can configure specific linters' options only within the config file (not the command-line).

There is a .golangci.example.yml example
config file with all supported options, their description and default value:

# This file contains all available configuration options
# with their default values.

# options for analysis running
run:
  # default concurrency is a available CPU number
  concurrency: 4

  # timeout for analysis, e.g. 30s, 5m, default is 1m
  deadline: 1m

  # exit code when at least one issue was found, default is 1
  issues-exit-code: 1

  # include test files or not, default is true
  tests: true

  # list of build tags, all linters use it. Default is empty list.
  build-tags:
    - mytag

  # which dirs to skip: they won't be analyzed;
  # can use regexp here: generated.*, regexp is applied on full path;
  # default value is empty list, but next dirs are always skipped independently
  # from this option's value:
  #   	vendor$, third_party$, testdata$, examples$, Godeps$, builtin$
  skip-dirs:
    - src/external_libs
    - autogenerated_by_my_lib

  # which files to skip: they will be analyzed, but issues from them
  # won't be reported. Default value is empty list, but there is
  # no need to include all autogenerated files, we confidently recognize
  # autogenerated files. If it's not please let us know.
  skip-files:
    - ".*\\.my\\.go$"
    - lib/bad.go

  # by default isn't set. If set we pass it to "go list -mod={option}". From "go help modules":
  # If invoked with -mod=readonly, the go command is disallowed from the implicit
  # automatic updating of go.mod described above. Instead, it fails when any changes
  # to go.mod are needed. This setting is most useful to check that go.mod does
  # not need updates, such as in a continuous integration and testing system.
  # If invoked with -mod=vendor, the go command assumes that the vendor
  # directory holds the correct copies of dependencies and ignores
  # the dependency descriptions in go.mod.
  modules-download-mode: readonly|release|vendor


# output configuration options
output:
  # colored-line-number|line-number|json|tab|checkstyle|code-climate, default is "colored-line-number"
  format: colored-line-number

  # print lines of code with issue, default is true
  print-issued-lines: true

  # print linter name in the end of issue text, default is true
  print-linter-name: true


# all available settings of specific linters
linters-settings:
  errcheck:
    # report about not checking of errors in type assetions: `a := b.(MyStruct)`;
    # default is false: such cases aren't reported by default.
    check-type-assertions: false

    # report about assignment of errors to blank identifier: `num, _ := strconv.Atoi(numStr)`;
    # default is false: such cases aren't reported by default.
    check-blank: false

    # [deprecated] comma-separated list of pairs of the form pkg:regex
    # the regex is used to ignore names within pkg. (default "fmt:.*").
    # see https://github.com/kisielk/errcheck#the-deprecated-method for details
    ignore: fmt:.*,io/ioutil:^Read.*

    # path to a file containing a list of functions to exclude from checking
    # see https://github.com/kisielk/errcheck#excluding-functions for details
    exclude: /path/to/file.txt

  funlen:
    lines: 60
    statements: 40

  govet:
    # report about shadowed variables
    check-shadowing: true

    # settings per analyzer
    settings:
      printf: # analyzer name, run `go tool vet help` to see all analyzers
        funcs: # run `go tool vet help printf` to see available settings for `printf` analyzer
          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Infof
          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Warnf
          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Errorf
          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Fatalf

    # enable or disable analyzers by name
    enable:
      - atomicalign
    enable-all: false
    disable:
      - shadow
    disable-all: false
  golint:
    # minimal confidence for issues, default is 0.8
    min-confidence: 0.8
  gofmt:
    # simplify code: gofmt with `-s` option, true by default
    simplify: true
  goimports:
    # put imports beginning with prefix after 3rd-party packages;
    # it's a comma-separated list of prefixes
    local-prefixes: github.com/org/project
  gocyclo:
    # minimal code complexity to report, 30 by default (but we recommend 10-20)
    min-complexity: 10
  maligned:
    # print struct with more effective memory layout or not, false by default
    suggest-new: true
  dupl:
    # tokens count to trigger issue, 150 by default
    threshold: 100
  goconst:
    # minimal length of string constant, 3 by default
    min-len: 3
    # minimal occurrences count to trigger, 3 by default
    min-occurrences: 3
  depguard:
    list-type: blacklist
    include-go-root: false
    packages:
      - github.com/sirupsen/logrus
    packages-with-error-messages:
      # specify an error message to output when a blacklisted package is used
      github.com/sirupsen/logrus: "logging is allowed only by logutils.Log"
  misspell:
    # Correct spellings using locale preferences for US or UK.
    # Default is to use a neutral variety of English.
    # Setting locale to US will correct the British spelling of 'colour' to 'color'.
    locale: US
    ignore-words:
      - someword
  lll:
    # max line length, lines longer will be reported. Default is 120.
    # '\t' is counted as 1 character by default, and can be changed with the tab-width option
    line-length: 120
    # tab width in spaces. Default to 1.
    tab-width: 1
  unused:
    # treat code as a program (not a library) and report unused exported identifiers; default is false.
    # XXX: if you enable this setting, unused will report a lot of false-positives in text editors:
    # if it's called for subdir of a project it can't find funcs usages. All text editor integrations
    # with golangci-lint call it on a directory with the changed file.
    check-exported: false
  unparam:
    # Inspect exported functions, default is false. Set to true if no external program/library imports your code.
    # XXX: if you enable this setting, unparam will report a lot of false-positives in text editors:
    # if it's called for subdir of a project it can't find external interfaces. All text editor integrations
    # with golangci-lint call it on a directory with the changed file.
    check-exported: false
  nakedret:
    # make an issue if func has more lines of code than this setting and it has naked returns; default is 30
    max-func-lines: 30
  prealloc:
    # XXX: we don't recommend using this linter before doing performance profiling.
    # For most programs usage of prealloc will be a premature optimization.

    # Report preallocation suggestions only on simple loops that have no returns/breaks/continues/gotos in them.
    # True by default.
    simple: true
    range-loops: true # Report preallocation suggestions on range loops, true by default
    for-loops: false # Report preallocation suggestions on for loops, false by default
  gocritic:
    # Which checks should be enabled; can't be combined with 'disabled-checks';
    # See https://go-critic.github.io/overview#checks-overview
    # To check which checks are enabled run `GL_DEBUG=gocritic golangci-lint run`
    # By default list of stable checks is used.
    enabled-checks:
      - rangeValCopy

    # Which checks should be disabled; can't be combined with 'enabled-checks'; default is empty
    disabled-checks:
      - regexpMust

    # Enable multiple checks by tags, run `GL_DEBUG=gocritic golangci-lint` run to see all tags and checks.
    # Empty list by default. See https://github.com/go-critic/go-critic#usage -> section "Tags".
    enabled-tags:
      - performance

    settings: # settings passed to gocritic
      captLocal: # must be valid enabled check name
        paramsOnly: true
      rangeValCopy:
        sizeThreshold: 32
  godox:
    # report any comments starting with keywords, this is useful for TODO or FIXME comments that
    # might be left in the code accidentally and should be resolved before merging
    keywords: # default keywords are TODO, BUG, and FIXME, these can be overwritten by this setting
      - NOTE
      - OPTIMIZE # marks code that should be optimized before merging
      - HACK # marks hack-arounds that should be removed before merging
  dogsled:
    # checks assignments with too many blank identifiers; default is 2
    max-blank-identifiers: 2

  whitespace:
    multi-if: false

linters:
  enable:
    - megacheck
    - govet
  enable-all: false
  disable:
    - maligned
    - prealloc
  disable-all: false
  presets:
    - bugs
    - unused
  fast: false


issues:
  # List of regexps of issue texts to exclude, empty list by default.
  # But independently from this option we use default exclude patterns,
  # it can be disabled by `exclude-use-default: false`. To list all
  # excluded by default patterns execute `golangci-lint run --help`
  exclude:
    - abcdef

  # Excluding configuration per-path, per-linter, per-text and per-source
  exclude-rules:
    # Exclude some linters from running on tests files.
    - path: _test\.go
      linters:
        - gocyclo
        - errcheck
        - dupl
        - gosec

    # Exclude known linters from partially hard-vendored code,
    # which is impossible to exclude via "nolint" comments.
    - path: internal/hmac/
      text: "weak cryptographic primitive"
      linters:
        - gosec

    # Exclude some staticcheck messages
    - linters:
        - staticcheck
      text: "SA9003:"

    # Exclude lll issues for long lines with go:generate
    - linters:
        - lll
      source: "^//go:generate "

  # Independently from option `exclude` we use default exclude patterns,
  # it can be disabled by this option. To list all
  # excluded by default patterns execute `golangci-lint run --help`.
  # Default value for this option is true.
  exclude-use-default: false

  # Maximum issues count per one linter. Set to 0 to disable. Default is 50.
  max-issues-per-linter: 0

  # Maximum count of issues with the same text. Set to 0 to disable. Default is 3.
  max-same-issues: 0

  # Show only new issues: if there are unstaged changes or untracked files,
  # only those changes are analyzed, else only changes in HEAD~ are analyzed.
  # It's a super-useful option for integration of golangci-lint into existing
  # large codebase. It's not practical to fix all existing issues at the moment
  # of integration: much better don't allow issues in new code.
  # Default is false.
  new: false

  # Show only new issues created after git revision `REV`
  new-from-rev: REV

  # Show only new issues created in git patch with set file path.
  new-from-patch: path/to/patch/file

It's a .golangci.yml config file of this repo: we enable more linters
than the default and have more strict settings:

linters-settings:
  govet:
    check-shadowing: true
    settings:
      printf:
        funcs:
          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Infof
          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Warnf
          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Errorf
          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Fatalf
  golint:
    min-confidence: 0
  gocyclo:
    min-complexity: 15
  maligned:
    suggest-new: true
  dupl:
    threshold: 100
  goconst:
    min-len: 2
    min-occurrences: 2
  depguard:
    list-type: blacklist
    packages:
      # logging is allowed only by logutils.Log, logrus
      # is allowed to use only in logutils package
      - github.com/sirupsen/logrus
    packages-with-error-messages:
      github.com/sirupsen/logrus: "logging is allowed only by logutils.Log"
  misspell:
    locale: US
  lll:
    line-length: 140
  goimports:
    local-prefixes: github.com/golangci/golangci-lint
  gocritic:
    enabled-tags:
      - performance
      - style
      - experimental
    disabled-checks:
      - wrapperFunc
      - dupImport # https://github.com/go-critic/go-critic/issues/845
  funlen:
    lines: 100
    statements: 50

linters:
  # inverted configuration with `enable-all` and `disable` is not scalable during updates of golangci-lint
  disable-all: true
  enable:
    - bodyclose
    - deadcode
    - depguard
    - dogsled
    - dupl
    - errcheck
    - funlen
    - gochecknoinits
    - goconst
    - gocritic
    - gocyclo
    - gofmt
    - goimports
    - golint
    - gosec
    - gosimple
    - govet
    - ineffassign
    - interfacer
    - lll
    - misspell
    - nakedret
    - scopelint
    - staticcheck
    - structcheck
    - stylecheck
    - typecheck
    - unconvert
    - unparam
    - unused
    - varcheck
    - whitespace

  # don't enable:
  # - godox
  # - maligned,prealloc
  # - gochecknoglobals

run:
  skip-dirs:
    - test/testdata_etc
    - internal/(cache|renameio|robustio)

issues:
  exclude-rules:
    - text: "weak cryptographic primitive"
      linters:
        - gosec

# golangci.com configuration
# https://github.com/golangci/golangci/wiki/Configuration
service:
  golangci-lint-version: 1.19.x # use the fixed version to not introduce new linters unexpectedly
  prepare:
    - echo "here I can run custom commands, but no preparation needed for this repo"

False Positives

False positives are inevitable, but we did our best to reduce their count. For example, we have a default enabled set of exclude patterns. If a false positive occurred you have the following choices:

  1. Exclude issue by text using command-line option -e or config option issues.exclude. It's helpful when you decided to ignore all issues of this type. Also, you can use issues.exclude-rules config option for per-path or per-linter configuration.
  2. Exclude this one issue by using special comment //nolint (see the section below).
  3. Exclude issues in path by run.skip-dirs, run.skip-files or issues.exclude-rules config options.

Please create GitHub Issues here if you find any false positives. We will add it to the default exclude list if it's common or we will fix underlying linter.

Nolint

To exclude issues from all linters use //nolint. For example, if it's used inline (not from the beginning of the line) it excludes issues only for this line.

var bad_name int //nolint

To exclude issues from specific linters only:

var bad_name int //nolint:golint,unused

To exclude issues for the block of code use this directive on the beginning of a line:

//nolint
func allIssuesInThisFunctionAreExcluded() *string {
  // ...
}

//nolint:govet
var (
  a int
  b int
)

Also, you can exclude all issues in a file by:

//nolint:unparam
package pkg

You may add a comment explaining or justifying why //nolint is being used on the same line as the flag itself:

//nolint:gocyclo // This legacy function is complex but the team too busy to simplify it
func someLegacyFunction() *string {
  // ...
}

You can see more examples of using //nolint in our tests for it.

Use //nolint instead of // nolint because machine-readable comments should have no space by Go convention.

FAQ

How do you add a custom linter?

You can integrate it yourself, see this wiki page with documentation. Or you can create a GitHub Issue and we will integrate when time permits.

It's cool to use golangci-lint when starting a project, but what about existing projects with large codebase? It will take days to fix all found issues

We are sure that every project can easily integrate golangci-lint, even the large one. The idea is to not fix all existing issues. Fix only newly added issue: issues in new code. To do this setup CI (or better use GolangCI) to run golangci-lint with option --new-from-rev=HEAD~1. Also, take a look at option --new, but consider that CI scripts that generate unstaged files will make --new only point out issues in those files and not in the last commit. In that regard --new-from-rev=HEAD~1 is safer.
By doing this you won't create new issues in your code and can choose fix existing issues (or not).

How to use golangci-lint in CI (Continuous Integration)?

You have 2 choices:

  1. Use GolangCI: this service is highly integrated with GitHub (issues are commented in the pull request) and uses a golangci-lint tool. For configuration use .golangci.yml (or toml/json).
  2. Use custom CI: just run golangci-lint in CI and check the exit code. If it's non-zero - fail the build. The main disadvantage is that you can't see issues in pull request code and would need to view the build log, then open the referenced source file to see the context.

We don't recommend vendoring golangci-lint in your repo: you will get troubles updating golangci-lint. Please, use recommended way to install with the shell script: it's very fast.

Do I need to run go install?

No, you don't need to do it anymore.

Which go versions are supported
Short answer: go 1.12 and newer are oficially supported.

Long answer:

  1. go < 1.9 isn't supported
  2. go1.9 is officially supported by golangci-lint <= v1.10.2
  3. go1.10 is officially supported by golangci-lint <= 1.15.0.
  4. go1.11 is officially supported by golangci-lint <= 1.17.1.
  5. go1.12+ are officially supported by the latest version of golangci-lint (>= 1.18.0).

golangci-lint doesn't work

  1. Update it: go get -u github.com/golangci/golangci-lint/cmd/golangci-lint
  2. Run it with -v option and check the output.
  3. If it doesn't help create a GitHub issue with the output from the error and #2 above.

Why running with --fast is slow on the first run?
Because the first run caches type information. All subsequent runs will be fast.
Usually this options is used during development on local machine and compilation was already performed.

Thanks

Thanks to all contributors!
Thanks to alecthomas/gometalinter for inspiration and amazing work.
Thanks to bradleyfalzon/revgrep for cool diff tool.

Thanks to developers and authors of used linters:

Changelog

Follow the news and releases on our twitter and our blog.
There is the most valuable changes log:

September 2019

  1. Support go1.13
  2. Add new linters: funlen, whitespace (with auto-fix) and godox
  3. Update linters: gochecknoglobals, scopelint, gosec
  4. Provide pre-built binary for ARM and FreeBSD
    1. Fix false-positives in unused
  5. Support --skip-dirs-use-default
  6. Add support for bash completions

July 2019

  1. Fix parallel writes race condition
  2. Update bodyclose with fixed panic

June 2019

  1. Treat Go source files as a plain text by misspell: it allows detecting issues in strings, variable names, etc.
  2. Implement richer and more stable auto-fix of misspell issues.

May 2019

  1. Add bodyclose linter.
  2. Support junit-xml output.

April 2019

  1. Update go-critic, new checkers were added: badCall, dupImports, evalOrder, newDeref
  2. Fix staticcheck panic on packages that do not compile
  3. Make install script work on Windows
  4. Fix compatibility with the latest x/tools version and update golang.org/x/tools
  5. Correct import path of module sourcegraph/go-diff
  6. Fix max-issues-per-linter name
  7. Fix linting of preprocessed files (e.g. *.qtpl.go, goyacc)
  8. Enable auto-fixing when running via pre-commit

March 2019

  1. Support the newest go vet (with go/analysis)
  2. Support configuration of go vet: e.g. you can set print functions by linters-settings.govet.settings.printf.funcs
  3. Update megacheck (staticcheck) to 2019.1.1
  4. Add information about controlling space-time trade-off into README
  5. Exclude issues by source code line regexp by issues.exclude-rules[i].source
  6. Build and test on go 1.12
  7. Support --color option
  8. Update x/tools to fix c++ issues
  9. Include support for log level
  10. Sort linters list in help commands

Debug

You can see a verbose output of linter by using -v option.

If you would like to see more detailed logs you can set environment variable GL_DEBUG to debug golangci-lint.
It's value is a list of debug tags. For example, GL_DEBUG=loader,gocritic golangci-lint run.
Existing debug tags:

  1. gocritic - debug go-critic linter;
  2. env - debug go env command;
  3. loader - debug packages loading (including go/packages internal debugging);
  4. autogen_exclude - debug a filter excluding autogenerated source code;
  5. nolint - debug a filter excluding issues by //nolint comments.

Future Plans

  1. Upstream all changes of forked linters.
  2. Make it easy to write own linter/checker: it should take a minimum code, have perfect documentation, debugging and testing tooling.
  3. Speed up SSA loading: on-disk cache and existing code profiling-optimizing.
  4. Analyze (don't only filter) only new code: analyze only changed files and dependencies, make incremental analysis, caches.
  5. Smart new issues detector: don't print existing issues on changed lines.
  6. Minimize false-positives by fixing linters and improving testing tooling.
  7. Automatic issues fixing (code rewrite, refactoring) where it's possible.
  8. Documentation for every issue type.

GitHub