appenv

What can it do

When we deploy in some service like AWS we often set our config in environment variables then retrieve it

value, exist := os.LookupEnv(envName)

However, we need to group these environment variables to a single struct and also need to handle default environment variables (most likely default variables for local developing).

By using struct tag we can define beauty config for our app

type config = struct {
	Port       uint16 `env:"APP_PORT" envDefault:"7000"`
	DBUser     string `env:"DB_USER" envDefault:"root"`
	DBPassword string `env:"DB_PASSWORD" envDefault:"root"`
	DBDefault  string `env:"DB_DEFAULT" envDefault:"awesome"`
	DBPort     uint16 `env:"DB_PORT" envDefault:"7706"`
}

When we use this config with the package, for example, field

Port       uint16 `env:"APP_PORT" envDefault:"7000"`

The package will set field Port with the environment variable APP_PORT if not found will use the default 7000. The default value or environment variable will be converted to correct type. In this case, it will be converted to uint16

How to use

Bear in mind the current folder structure just for my app. Your project structure might be different than mine.

First, define a config

File project/app/config.go

package app

var Config config

type config = struct {
	Port       uint16 `env:"APP_PORT" envDefault:"7000"`
	DBUser     string `env:"DB_USER" envDefault:"root"`
	DBPassword string `env:"DB_PASSWORD" envDefault:"root"`
	DBDefault  string `env:"DB_DEFAULT" envDefault:"awesome"`
	DBPort     uint16 `env:"DB_PORT" envDefault:"7706"`
}

Then use it in you main file

File project/main.go

package main

import (
	"github.com/gndplayground/appenv"
	"project/app"
)

func main() {

	appenv.Init(&app.Config)

	app.DBInit()

  ...
}

Then other package in app can use the config

File project/app/db.go

func DBInit() {
	var err error

	DB, err = gorm.Open("mysql", fmt.Sprintf(
		"%v:%v@(localhost:%v)/%v?charset=utf8&parseTime=True",
		Config.DBUser,
		Config.DBPassword,
		Config.DBPort,
		Config.DBDefault))

	defer func() {
		if err != nil {
			DB.Close()
			panic(err)
		}
	}()
}

Support Type

type config struct {
		Uint         uint      `env:"TEST_ENV_Uint" envDefault:"10"`
		Uint8        uint8     `env:"TEST_ENV_Uint8" envDefault:"10"`
		Uint16       uint16    `env:"TEST_ENV_Uint16" envDefault:"10"`
		Uint32       uint32    `env:"TEST_ENV_Uint32" envDefault:"10"`
		Uint64       uint64    `env:"TEST_ENV_Uint64" envDefault:"10"`
		Int          int       `env:"TEST_ENV_Int" envDefault:"-10"`
		Int8         int8      `env:"TEST_ENV_Int8" envDefault:"-10"`
		Int16        int16     `env:"TEST_ENV_Int16" envDefault:"-10"`
		Int32        int32     `env:"TEST_ENV_Int32" envDefault:"-10"`
		Int64        int64     `env:"TEST_ENV_Int64" envDefault:"-10"`
		Float32      float32   `env:"TEST_ENV_FLOAT32" envDefault:"3.2"`
		Float64      float64   `env:"TEST_ENV_FLOAT32" envDefault:"6.5"`
		String       string    `env:"TEST_ENV_STRING" envDefault:"hello"`
		ArrayString  []string  `env:"TEST_ENV_ArrayString" envDefault:"a,b,c"`
		ArrayBool    []bool    `env:"TEST_ENV_ArrayBool" envDefault:"true,true,false"`
		ArrayFloat64 []float64 `env:"TEST_ENV_ArrayFloat64" envDefault:"5.4,5.1,5.3"`
		ArrayFloat32 []float32 `env:"TEST_ENV_ArrayFloat32" envDefault:"5.4,5.1,5.3"`
		ArrayUint    []uint    `env:"TEST_ENV_ArrayUint" envDefault:"1,3,5"`
		ArrayUint8   []uint8   `env:"TEST_ENV_ArrayUint8" envDefault:"1,3,5"`
		ArrayUint16  []uint16  `env:"TEST_ENV_ArrayUint16" envDefault:"1,3,5"`
		ArrayUint32  []uint32  `env:"TEST_ENV_ArrayUint32" envDefault:"1,3,5"`
		ArrayUint64  []uint64  `env:"TEST_ENV_ArrayUint64" envDefault:"1,3,5"`
		ArrayInt     []int     `env:"TEST_ENV_ArrayInt" envDefault:"1,-3,5"`
		ArrayInt8    []int8    `env:"TEST_ENV_ArrayInt8" envDefault:"1,-3,5"`
		ArrayInt16   []int16   `env:"TEST_ENV_ArrayInt16" envDefault:"1,-3,5"`
		ArrayInt32   []int32   `env:"TEST_ENV_ArrayInt32" envDefault:"1,-3,5"`
		ArrayInt64   []int64   `env:"TEST_ENV_ArrayInt64" envDefault:"1,-3,5"`
	}