Mconfig

Mconfig is a lightweight Golang library for integrating configs files like (json, yml, toml) and environment variables into one config struct.

Features

• Load multiple types of files (yaml, json, toml).
• Autofill environment variables with .env files.
• Works with nested structs.
• Combine config files and environment variables.
• Map environment variables to struct via tag.
• Auto casting.
• Easy to use (only one function exposed).
• Extendable (allows add more providers).
• Customizable (via facade).

Usage

Mconfig is designed to be very simple and straightforward to use. All you can do with it is load configurations to a predifined struct.

First define a configuration structure:

type MysqlConfiguration struct {
    Host     string `env:"MYSQL_HOST"`
    Username string `env:"MYSQL_USERNAME"`
    Password string `env:"MYSQL_PASSWORD"`
    Database string `env:"MYSQL_DATABASE"`
    Port     int    `env:"MYSQL_PORT"`
}

type RedisConfiguration struct {
    Host string `env:"REDIS_HOST"`
    Port int    `env:"REDIS_PORT"`
}

type Configuration struct {
    Port         int `env:"APP_PORT"`
    Mysql        MysqlConfiguration
    Redis        RedisConfiguration
}

Then fill your YAML (config.yaml) file:

---
Port: 3001
Mysql:
  Host: 192.168.0.1
  Username: root
  Password: test
  Database: mconfig
  Port: 3306
Redis:
  Host: localhost
  Port: 6379

From your code:

import 	"github.com/jmartin82/mconfig/pkg/mconfig"

configuration := Configuration{}
err := mconfig.Parse("config.yaml", &configuration)
if err != nil {
	panic(err)
}

Finally in prod:

MYSQL_PASSWORD=SuperSecret MYSQL_HOST=mysql.prod.service REDIS_HOST=mysql.prod.service your_app

Supported types

All environment variables are string but you can specify the correct type in your configuration struct.

The valid types are:

type TestTypes struct {
	IsInt        int      `env:"FOO_VAR"`
	IsUint       uint     `env:"FOO_VAR"`
	IsString     string   `env:"FOO_VAR"`
	IsFloat      float64  `env:"FOO_VAR"`
	IsBool       bool     `env:"FOO_VAR"`
	PtrIsInt     *int     `env:"FOO_VAR"`
	PtrIsInt8    *int8    `env:"FOO_VAR"`
	PtrIsInt16   *int16   `env:"FOO_VAR"`
	PtrIsInt32   *int32   `env:"FOO_VAR"`
	PtrIsInt64   *int64   `env:"FOO_VAR"`
	PtrIsUint    *uint    `env:"FOO_VAR"`
	PtrIsUint8   *uint8   `env:"FOO_VAR"`
	PtrIsUint16  *uint16  `env:"FOO_VAR"`
	PtrIsUint32  *uint32  `env:"FOO_VAR"`
	PtrIsUint64  *uint64  `env:"FOO_VAR"`
	PtrIsString  *string  `env:"FOO_VAR"`
	PtrIsFloat32 *float32 `env:"FOO_VAR"`
	PtrIsFloat64 *float64 `env:"FOO_VAR"`
        PtrIsBool    *bool    `env:"FOO_VAR"`
        Struct       struct
        PtrStruct    *struct
}

In case of an casting error, the field will keep the original value.

Customization

By default only the Parse function it's exposed. With that, you can read json, yaml, toml. Load .env files and combine the config read from the file with your system environment variables.

But if you don't want the full feature call, you always can use the facade to adjust the functionality to your necessities.

Read-only env vars from your system and load into your config struct.

import 	"github.com/jmartin82/mconfig/pkg/mconfig"

configuration := Configuration{}
err := mconfig.ConfigManager.ReadFromEnvironment(&configuration);
if err != nil {
	panic(err)
}

Read only the config from a toml.

import 	"github.com/jmartin82/mconfig/pkg/mconfig"

configuration := Configuration{}
err := mconfig.ConfigManager.ReadFromFile("config.toml", &configuration)
if err != nil {
	panic(err)
}

Use differnt files to load the enviroment variables.

import 	"github.com/jmartin82/mconfig/pkg/mconfig"

configuration := Configuration{}
mconfig.ConfigManager.SetEnvFiles("enviroment.txt","env.txt")
err := mconfig.Parse("config.yaml", &configuration)
if err != nil {
	panic(err)
}

Extensibility

You can add more file provider in order to read different kind of config files.

Interface:

type Unmarshaler interface {
	IsCapable(filename string) bool
	Unmarshal(source []byte, configuration interface{}) error
}

Code:

import 	"github.com/jmartin82/mconfig/pkg/mconfig"

configuration := Configuration{}
mconfig.ConfigManager.AddFileUnmashaler(NewXMLFormatUnmarshaler())
err := mconfig.Parse("config.yaml", &configuration)
if err != nil {
	panic(err)
}

Current limitations

• Only the exposed fields can be setted via file config or enviroment variable.
• The config struct should be a pointer.

Licence

Copyright © 2018 - 2018, Jordi Martín (http://jordi.io)

Released under MIT license, see LICENSE for details.