Programming language: Go
License: MIT License
Tags: Configuration    

envcfg alternatives and similar packages

Based on the "Configuration" category.
Alternatively, view envcfg alternatives based on common mentions on social networks and blogs.

Do you think we are missing an alternative of envcfg or a related project?

Add another 'Configuration' Package


envcfg Build Status

Un-marshaling environment variables to Go structs

Getting Started

Let's set a bunch of environment variables and then run your go app

#!/usr/bin/env bash
export DEBUG="false"
export DB_HOST="localhost"
export DB_PORT="8012"


Within your Go app do

import "github.com/tomazk/envcfg"

// declare a type that will hold your env variables
type Cfg struct {
    DEBUG   bool
    DB_PORT int
    DB_HOST string

func main() {
    var config Cfg
    // config is now set to Config{DEBUG: false, DB_PORT: 8012, DB_HOST: "localhost"}

    // optional: clear env variables listed in the Cfg struct


$ go get github.com/tomazk/envcfg


As per 12 factor app manifesto configuration of an app should be stored in the environment since it varies between environments by nature. This convention is also dicated and popularized by emerging technologies like docker and cloud platforms.

Instead of having a bunch of os.Getenv("ENV_VAR") buried deep in your code when configuring clients and services, envcfg encourages you to:

  1. define a struct type that will hold your environment variables and serve as documentation which env variables must be configured
  2. use envcfg.Unmarshal to read your env variables and unmarhsal them to an object that now holds your configuration of an app
  3. use envcfg.ClearEnvVars to unset env variables, removing potential vulnerability of passing secrets to unsafe child processes or vendor libraries that assume you're not storing unsafe values in the environment



func Unmarshal(v interface{}) error can recieve a reference to an object or even a reference to a pointer:

var val2 StructType

var val1 *StructType 
envcfg.Unmarshal(&val1) // val1 will be initialized

Supported Struct Field Types

envcfg.Unmarshal supports int, string, bool and []int, []string, []bool types of fields wihin a struct. In addition, fields that satisfy the encoding.TextUnmarshaler interface are also supported. envcfg.Unmarshal will return nil if a valid struct was passed or return an error if not.

type StructType struct {
    INT           int
    BOOL          bool
    STRING        string
    SLICE_STRING  []string
    SLICE_BOOL    []bool
    SLICE_INT     []int
    CUSTOM_TYPE   MyType

type MyType struct{}
func (mt *MyType) UnmarshalText(text []byte) error {


envcfg.Unmarshal also spares you from writing type validation code:

type StructType struct {

If you'll pass export SHOULD_BE_INT="some_string_value" to your application envcfg.Unmarshal will return an error.

Struct Tags for Custom Mapping of env Variables

You can also use struct field tags to map env variables to fields wihin a struct

export MY_ENV_VAR=1
type StructType struct {
    Field int `envcfg:"MY_ENV_VAR"`

Slices Support

envcfg.Unmarshal also supports []int, []string, []bool slices. Values of the slice are ordered in respect to env name suffix. See example below.

export CASSANDRA_HOST_1="" # *_1 will come as the first element of the slice
export CASSANDRA_HOST_2=""
export CASSANDRA_HOST_3=""
type StructType struct {
    CASSANDRA_HOST []string
func main() {
    var config StructType
    // config.CASSANDRA_HOST is now set to []string{"", "", ""} 


func ClearEnvVars(v interface{}) error recieves a reference to the same struct you've passed to envcfg.Unmarshal and it will unset any environment variables listed in the struct. Except for those that you want to keep and are tagged with envcfgkeep:"" struct field tag. It will throw an error on unsupported types.

export SECRET_AWS_KEY="foobar" 
export PORT="8080" 
type StructType struct {
    SECRET_AWS_KEY string
    PORT           int    `envcfgkeep:""`
func main() {
    var config StructType
    // it will unset SECRET_AWS_KEY but keep env variable PORT


Send me a pull request and make sure tests pass on travis.


Package comes with an extensive test suite that's continuously run on travis against go versions: 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 and the development tip.

$ go test github.com/tomazk/envcfg


See LICENCE file