Programming language: Go
License: MIT License
Tags: Configuration    
Latest version: v2.0.18

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config - Simple, full-featured Go application configuration management tool library.



  • Support multi format: JSON(default), JSON5, INI, Properties, YAML, TOML, HCL, ENV, Flags
    • JSON content support comments. will auto clear comments
    • Other drivers are used on demand, not used will not be loaded into the application.
    • Possibility to add custom driver for your specific format
  • Support multi-file and multi-data loading
  • Support for loading configuration from system ENV
  • Support for loading configuration data from remote URLs
  • Support for setting configuration data from command line(flags)
  • Support listen and fire events on config data changed.
    • allow events: set.value, set.data, load.data, clean.data, reload.data
  • Support data overlay and merge, automatically load by key when loading multiple copies of data
  • Support for binding all or part of the configuration data to the structure
    • Support init default value by struct tag default:"def_value"
    • Support init default value from ENV default:"${APP_ENV | dev}"
  • Support get sub value by key-path, like map.key arr.2
  • Support parse ENV name and allow with default value. like envKey: ${SHELL|/bin/bash} -> envKey: /bin/zsh
  • Generic API: Get Int Uint Int64 Float String Bool Ints IntMap Strings StringMap ...
  • Complete unit test(code coverage > 95%)

Only use INI

If you just want to use INI for simple config management, recommended use gookit/ini

Load dotenv file

On gookit/ini: Provide a sub-package dotenv that supports importing data from files (eg .env) to ENV

go get github.com/gookit/ini/v2/dotenv



go get github.com/gookit/config/v2


Here using the yaml format as an example(testdata/yml_other.yml):

name: app2
debug: false
baseKey: value2
shell: ${SHELL}
envKey1: ${NotExist|defValue}

    key: val2
    key2: val20

    - val1
    - val21

Load data

examples code please see [_examples/yaml.go](_examples/yaml.go):

package main

import (

// go run ./examples/yaml.go
func main() {

    // add driver for support yaml content

    err := config.LoadFiles("testdata/yml_base.yml")
    if err != nil {

    // load more files
    err = config.LoadFiles("testdata/yml_other.yml")
    // can also load multi at once
    // err := config.LoadFiles("testdata/yml_base.yml", "testdata/yml_other.yml")
    if err != nil {

    // fmt.Printf("config data: \n %#v\n", config.Data())

Usage tips:

  • More extra options can be added using WithOptions(). For example: ParseEnv, ParseDefault
  • You can use AddDriver() to add the required format driver (json is loaded by default, no need to add)
  • The configuration data can then be loaded using LoadFiles() LoadStrings() etc.
    • You can pass in multiple files or call multiple times
    • Data loaded multiple times will be automatically merged by key

Bind Structure

Note: The default binding mapping tag of a structure is mapstructure, which can be changed by setting the decoder's option options.DecoderConfig.TagName

type User struct {
    Age  int  `mapstructure:"age"`
    Key  string `mapstructure:"key"`
    UserName  string `mapstructure:"user_name"`
    Tags []int  `mapstructure:"tags"`

user := User{}
err = config.BindStruct("user", &user)

fmt.Println(user.UserName) // inhere

Change struct tag name

config.WithOptions(func(opt *Options) {
    options.DecoderConfig.TagName = "config"

// use custom tag name.
type User struct {
  Age  int  `config:"age"`
  Key  string `config:"key"`
  UserName  string `config:"user_name"`
  Tags []int  `config:"tags"`

user := User{}
err = config.Decode(&user)

Can bind all config data to a struct:

// can also
config.BindStruct("", &myConf)

config.MapOnExists like BindStruct,but map binding only if key exists

Direct read data

  • Get integer
age := config.Int("age")
fmt.Print(age) // 100
  • Get bool
val := config.Bool("debug")
fmt.Print(val) // true
  • Get string
name := config.String("name")
fmt.Print(name) // inhere
  • Get strings(slice)
arr1 := config.Strings("arr1")
fmt.Printf("%#v", arr1) // []string{"val1", "val21"}
  • Get string map
val := config.StringMap("map1")
fmt.Printf("%#v",val) // map[string]string{"key":"val2", "key2":"val20"}
  • Value contains ENV var
value := config.String("shell")
fmt.Print(value) // "/bin/zsh"
  • Get value by key path
// from array
value := config.String("arr1.0")
fmt.Print(value) // "val1"

// from map
value := config.String("map1.key")
fmt.Print(value) // "val2"
  • Setting new value
// set value
config.Set("name", "new name")
name = config.String("name")
fmt.Print(name) // "new name"

Load from flags

Support simple flags parameter parsing, loading

// flags like: --name inhere --env dev --age 99 --debug

// load flag info
keys := []string{"name", "env", "age:int" "debug:bool"}
err := config.LoadFlags(keys)

// read
config.String("name") // "inhere"
config.String("env") // "dev"
config.Int("age") // 99
config.Bool("debug") // true

Load from ENV

// os env: APP_NAME=config APP_DEBUG=true
// load ENV info
config.LoadOSEnvs(map[string]string{"APP_NAME": "app_name", "APP_DEBUG": "app_debug"})

// read
config.Bool("app_debug") // true
config.String("app_name") // "config"

New config instance

You can create custom config instance

// create new instance, will auto register JSON driver
myConf := config.New("my-conf")

// create empty instance
myConf := config.NewEmpty("my-conf")

// create and with some options
myConf := config.NewWithOptions("my-conf", config.ParseEnv, config.ReadOnly)

Listen config change

Now, you can add a hook func for listen config data change. then, you can do something like: write data to file

Add hook func on create config:

hookFn := func(event string, c *Config) {
    fmt.Println("fire the:", event)

c := NewWithOptions("test", config.WithHookFunc(hookFn))
// for global config

After that, when calling LoadXXX, Set, SetData, ClearData methods, it will output:

fire the: load.data
fire the: set.value
fire the: set.data
fire the: clean.data

Watch loaded config files

To listen for changes to loaded config files, and reload the config when it changes, you need to use the https://github.com/fsnotify/fsnotify library. For usage, please refer to the example [./_example/watch_file.go](_examples/watch_file.go)

Also, you need to listen to the reload.data event:

config.WithOptions(config.WithHookFunc(func(event string, c *config.Config) {
    if event == config.OnReloadData {
        fmt.Println("config reloaded, you can do something ....")

When the configuration changes, you can do related things, for example: rebind the configuration to your struct.

Dump config data

Can use config.DumpTo() export the configuration data to the specified writer, such as: buffer,file

Dump to JSON file

buf := new(bytes.Buffer)

_, err := config.DumpTo(buf, config.JSON)
ioutil.WriteFile("my-config.json", buf.Bytes(), 0755)

Dump pretty JSON

You can set the default var JSONMarshalIndent or custom a new JSON driver.

config.JSONMarshalIndent = "    "

Dump to YAML file

_, err := config.DumpTo(buf, config.YAML)
ioutil.WriteFile("my-config.yaml", buf.Bytes(), 0755)

Available options

// Options config options
type Options struct {
    // parse env value. like: "${EnvName}" "${EnvName|default}"
    ParseEnv bool
    // ParseTime parses a duration string to time.Duration
    // eg: 10s, 2m
    ParseTime bool
    // config is readonly. default is False
    Readonly bool
    // enable config data cache. default is False
    EnableCache bool
    // parse key, allow find value by key path. default is True eg: 'key.sub' will find `map[key]sub`
    ParseKey bool
    // tag name for binding data to struct
    // Deprecated
    // please set tag name by DecoderConfig
    TagName string
    // the delimiter char for split key path, if `FindByPath=true`. default is '.'
    Delimiter byte
    // default write format
    DumpFormat string
    // default input format
    ReadFormat string
    // DecoderConfig setting for binding data to struct
    DecoderConfig *mapstructure.DecoderConfig
    // HookFunc on data changed.
    HookFunc HookFunc
    // ParseDefault tag on binding data to struct. tag: default
    ParseDefault bool

Options: Parse default

Support parse default value by struct tag default

// add option: config.ParseDefault
c := config.New("test").WithOptions(config.ParseDefault)

// only set name
    "name": "inhere",

// age load from default tag
type User struct {
    Age  int `default:"30"`
    Name string
    Tags []int

user := &User{}


&config_test.User {
  Age: int(30),
  Name: string("inhere"), #len=6
  Tags: []int [ #len=0

API Methods Refer

Load Config

  • LoadOSEnvs(nameToKeyMap map[string]string) Load data from os ENV
  • LoadData(dataSource ...interface{}) (err error) Load from struts or maps
  • LoadFlags(keys []string) (err error) Load from CLI flags
  • LoadExists(sourceFiles ...string) (err error)
  • LoadFiles(sourceFiles ...string) (err error)
  • LoadFromDir(dirPath, format string) (err error) Load custom format files from the given directory, the file name will be used as the key
  • LoadRemote(format, url string) (err error)
  • LoadSources(format string, src []byte, more ...[]byte) (err error)
  • LoadStrings(format string, str string, more ...string) (err error)
  • LoadFilesByFormat(format string, sourceFiles ...string) (err error)
  • LoadExistsByFormat(format string, sourceFiles ...string) error

Getting Values

  • Bool(key string, defVal ...bool) bool
  • Int(key string, defVal ...int) int
  • Uint(key string, defVal ...uint) uint
  • Int64(key string, defVal ...int64) int64
  • Ints(key string) (arr []int)
  • IntMap(key string) (mp map[string]int)
  • Float(key string, defVal ...float64) float64
  • String(key string, defVal ...string) string
  • Strings(key string) (arr []string)
  • SubDataMap(key string) maputi.Data
  • StringMap(key string) (mp map[string]string)
  • Get(key string, findByPath ...bool) (value interface{})

Mapping data to struct:

  • Decode(dst any) error
  • BindStruct(key string, dst any) error
  • MapOnExists(key string, dst any) error

Setting Values

  • Set(key string, val interface{}, setByPath ...bool) (err error)

Useful Methods

  • Getenv(name string, defVal ...string) (val string)
  • AddDriver(driver Driver)
  • Data() map[string]interface{}
  • SetData(data map[string]interface{}) set data to override the Config.Data
  • Exists(key string, findByPath ...bool) bool
  • DumpTo(out io.Writer, format string) (n int64, err error)

Run Tests

go test -cover
// contains all sub-folder
go test -cover ./...

Projects using config

Check out these projects, which use https://github.com/gookit/config :

Gookit packages

  • gookit/ini Go config management, use INI files
  • gookit/rux Simple and fast request router for golang HTTP
  • gookit/gcli build CLI application, tool library, running CLI commands
  • gookit/event Lightweight event manager and dispatcher implements by Go
  • gookit/cache Generic cache use and cache manager for golang. support File, Memory, Redis, Memcached.
  • gookit/config Go config management. support JSON, YAML, TOML, INI, HCL, ENV and Flags
  • gookit/color A command-line color library with true color support, universal API methods and Windows support
  • gookit/filter Provide filtering, sanitizing, and conversion of golang data
  • gookit/validate Use for data validation and filtering. support Map, Struct, Form data
  • gookit/goutil Some utils for the Go: string, array/slice, map, format, cli, env, filesystem, test and more
  • More, please see https://github.com/gookit

See also



*Note that all licence references and agreements mentioned in the gookit/config README section above are relevant to that project's source code only.