envconf

Tiny environment variable mapper for golang

Getting Started

Prerequisites

Go 1.11+

Installing

$ go get -u github.com/akito0107/envconf

Examples

Simple mapping case

set environment variables.

export DB_HOST=localhost
export DB_PORT=5432

and implement Go code like this

package main

import (
	"log"

	"github.com/akito0107/envconf"
)

// struct with `env` tagged literal
type Config struct {
    DBHost string `env:"DB_HOST"` // 
    DBPort int `env:"DB_PORT"`
}

func main() {
    var conf Config
    
    // load environment variables with `Load` method
    if err := envconf.Load(&conf); err != nil {
    	log.Fatal(err)
    }
    
    log.Printf("%+v\n", conf) // should be `{DBHost:localhost DBPort:5432}`
}

You can confirm that variables are mapped to struct via envconf.Load.

$ go run main.go
2019/03/01 16:46:14 {DBHost:localhost DBPort:5432}

Blank environment variables

envconf.Load, in default behaviour, returns error when specified environment variables are blank. If missing DB_PORT variable, returns error.

$ export DB_HOST=localhost
$ go run main.go
2019/03/01 16:49:56 init: relpaceEnv failed: environmentVariableNotFound Envname: DB_PORT
exit status 1

Allow Empty

If you want to allow empty variables, you must specify allow-empty on env tag. This feature convenient for setting default parameter.

// struct with `env` tagged literal
type Config struct {
	DBHost string `env:"DB_HOST"`
	DBPort int    `env:"DB_PORT,allow-empty"` // set allow-empty
}

....
	
var conf Config

	// load environment variables with `Load` method
if err := envconf.Load(&conf); err != nil {
	log.Fatal(err) // should not be error
}

log.Printf("%+v\n", conf) // 2019/03/01 16:57:57 {DBHost:localhost DBPort:0}

conf2 := Config{DBPort: 12345} // passing default param

// load environment variables with `Load` method
if err := envconf.Load(&conf2); err != nil {
	log.Fatal(err)
}

log.Printf("%+v\n", conf2) // 2019/03/01 16:57:57 {DBHost:localhost DBPort:12345}

with Dotenv

envconf support using with dotenv by passing UseDotEnv option.

In default case, .env vars override environment variables

Go code.

// load environment variables and dotenv variables with `Load` method
if err := envconf.Load(&conf, envconf.UseDotEnv()); err != nil {
	log.Fatal(err)
}
log.Printf("%+v\n", conf)

$ cat .env
DB_USER=test

$ export DB_HOST=localhost
$ export DB_PORT=5432
$ export DB_USER=test2
$ go run main.go
2019/03/01 17:15:31 {DBHost:localhost DBPort:5432 DBUser:test} # overrided .env

disable Dotenv via ENVCONF_LOAD_DOTFILE environment variables

if ENVCONF_LOAD_DOTFILE is set to disable, skip load .env. This feature convenient for avoid to set undesired vars from .env.

$ cat .env
DB_USER=test

$ export ENVCONF_LOAD_DOTFILE=disable
$ export DB_HOST=localhost
$ export DB_PORT=5432
$ export DB_USER=test2
$ go run main.go
2019/03/01 17:15:31 {DBHost:localhost DBPort:5432 DBUser:test2} # overrided .env

License

This project is licensed under the Apache License 2.0 License - see the LICENSE file for details

akito0107 / envconf