fig loads your config file into a struct with additional support for marking fields as required and setting defaults.

Why fig?

  • Define your config, validations and defaults all in a single struct
  • Full support fortime.Time & time.Duration
  • Only 3 external dependencies
  • Tiny API
  • Decoders for .yaml, .json and .toml files

Getting Started

$ go get -d

Define your config file:

# config.yaml

build: "2020-01-09T12:30:00Z"

      - 8080
    cleanup: 1h

    level: "warn"
    trace: true

Define your struct along with any required and default fields:

package main

import (


type Config struct {
  Build  time.Time `fig:"build,required"`
  Server struct {
    Host    string        `fig:"host,default="`
    Ports   []int         `fig:"ports,default=[80,443]"`
    Cleanup time.Duration `fig:"cleanup,default=30m"`
  Logger struct {
    Level string `fig:"level,default=info"`
    Trace bool   `fig:"trace"`

func main() {
  var cfg Config
  err := fig.Load(&cfg)
  // handle your err
  fmt.Printf("%+v\n", cfg)
  // Output: {Build:2019-12-25 00:00:00 +0000 UTC Server:{Host: Ports:[8080] Cleanup:1h0m0s} Logger:{Level:warn Trace:true}}

If a field is not loaded from the config file and is marked as required then an error is returned. If a default value is defined instead then that value is used to populate the field.

Fig searches for a file named config.yaml in the directory it is run from. Change the lookup behaviour by passing additional parameters to Load():

  fig.Dirs(".", "/etc/myapp", "/home/user/myapp"),
) // searches for ./settings.json, /etc/myapp/settings.json, /home/user/myapp/settings.json