Binding configuration and command flag made easy!

You can use multiple keys tag to simplify the look like this (supported feature**):

// single tag key
type MyConfig struct {
    Token string `json:token_json" xml:"token_xml" arg:"token" env:"token" environ:"TOKEN"`
// multiple tag keys
type MyConfig struct {
    Token string `json xml bson yaml toml arg env:"token" environ:"TOKEN"`

Below is default mapping implementation of binder.RegisterCmdArgs = defaultRegisterCmdArgsFlagStd that use standard golang flag package to perform command flag.

The is a placeholder for parent key, binder.BindArgs(Loaded, "my") this case will be replaced with my, if there’s field with type struct in the component, it’ll be replaced to my..

Tag Go Code Description
arg:"token" flag.StringVar(val, ".token", *val, argUsage) Used for binding flag with contextual key
argx:"token" flag.StringVar(val, "token", *val, argUsage) Used for binding flag
bind:"log" No equivalent Used for binder to differ struct parent sub context .log.
env:"token" os env(".token") Used for binding to environment variable with contextual key
environ:"token" os env("token") Used for binding to environment
usage:"" Used as argUsage Description for flag


  • arg and argx (dedicated) basically has same function.
  • env and environ (dedicated) basically has same function.
  • Currently you can’t have dedicated key for configuration because the way it parsed is from Unmarshaller that results in map[string]interface{}, but this definitely possible to implement.

More thing you can learn from the example below.


package main

import (


type MyConfig struct {
    Token string `json xml bson yaml toml arg:"token,omitempty" env:"TOKEN" environ:"TOKEN"`
    Count int    `json xml bson yaml toml arg:"count,omitempty" env:"COUNT" usage:"this is the usage"`

    Ktes *int
    Sub  **struct {
        Hello    *string
        SubOfSub struct {
            InSub **bool
        PtrOfSub *struct {
            YourName **string `json xml bson yaml toml bind:"your_name,omitempty" env:"COUNT" usage:"this is the usage"`
    Log struct {
        SubLog       int
        Directory    string
        Filename     string `json xml bson yaml toml arg:"filename" env:"FILENAME"`
        DedicatedArg string `json xml bson yaml toml argx:"dedicatedArg" env:"DEDICATED_ARG"`
    } `json xml bson yaml toml arg env bind:"log"`
var (
    configFile = os    env("CONFIG_FILE")
    Loaded     *MyConfig

func registerToBinder() {
    Loaded = &MyConfig{
        Token: "some default value",
        Count: 121,
    binder.BindArgsConf(Loaded, "my")

func main() {
    var err error
    if configFile == "" {
        configFile = "config.json"
    binder.LoadConfig = binder.LoadConfigJSON(configFile)
    binder.SaveConfig = binder.SaveConfigJSON(configFile)
    binder.SaveOnClose = true
    // register component to binder
    // perform binding
    if err = binder.Init(); err != nil {
        if errors.Is(err, os.ErrNotExist) {
            if err = binder.Save(); err != nil {
        } else {
    // reflect back to component
    defer binder.Close()

    // runtime
    fmt.Printf("%+#v\n", Loaded)

Output help:

$ main -h
Usage of main:
  -dedicatedArg string

  -my.Sub.Hello string

  -my.count int
        this is the usage (default 121)
  -my.log.Directory string

  -my.log.filename string

  -my.token string
         (default "some default value")

Output JSON:

    "my": {
        "token": "some default value",
        "count": 121,
        "Ktes": 0,
        "Sub": {
            "Hello": "",
            "SubOfSub": {
                "InSub": false
            "PtrOfSub": {
                "your_name": ""
        "log": {
            "SubLog": 0,
            "Directory": "",
            "filename": "",
            "dedicatedArg": ""

Output TOML:

  token = "some default value"
  count = 121
  Ktes = 0
    Hello = ""
      InSub = false
      your_name = ""
    SubLog = 0
    Directory = ""
    filename = ""
    dedicatedArg = ""

Output YAML:

  token: some default value
  count: 121
  ktes: 0
    hello: ""
      insub: false
      your_name: ""
    sublog: 0
    directory: ""
    filename: ""
    dedicatedArg: ""


Contributions are welcome

**) Reverted feature as from 1.16 but found it useful


License: MIT