enviper

Package enviper is a helper/wrapper for viper with the same API. It makes it possible to unmarshal config to struct considering environment variables.

Attention : this repository is a fork for specific purpose. Use it only if you absolutely need to override map values with environment variables.

Otherwise, you should use the main repository https://github.com/iamolegga/enviper

Problem

Viper package doesn't consider environment variables while unmarshaling. Please, see: 188 and 761

Solution

Just wrap viper instance and use the same Unmarshal method as you did before:

e := enviper.New(viper.New())
e.Unmarshal(&config)

Example

package main

import (
	"github.com/iamolegga/enviper"
	"github.com/spf13/viper"
)

type barry struct {
    Bar int `mapstructure:"bar"`
}
type bazzy struct {
    Baz bool
}
type config struct {
    Foo string
    Barry barry
    Barries map[string]barry
    Bazzy bazzy `mapstructure:",squash"`
}

// For example this kind of structure can be unmarshaled with next yaml:
//  Foo: foo
//  Barry:
//    bar: 42
//  Baz: true
//  Barries: 
//    key1:
//      Bar: 255
//    key2:
//      Bar: 256
//
// And then it could be overriden by next env variables:
//  FOO=foo
//  BARRY_BAR=42
//  BAZ=true
//  BARRIES_KEY1_BAR=42
//
// Or with prefix:
//  MYAPP_FOO=foo
//  MYAPP_BARRY_BAR=42
//  MYAPP_BAZ=true
//  MYAPP_BARRIES_KEY1_BAR=42

func main() {    
    var c config

    e := enviper.New(viper.New())
    e.SetEnvPrefix("MYAPP")
    e.AddConfigPath("/my/config/path")
    e.SetConfigName("config")

    e.Unmarshal(&c)
}

Credits

Thanks to krak3n (issuecomment-399884438) and celian-garcia (issuecomment-626122696) for inspiring.

Thanks to iamolegga for taking the time to create this enviper library.