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

package main

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

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

// 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
//  Quxxy:
//    Qux: "lorem"
//
// And then it could be overriden by next env variables:
//  FOO=foo
//  BARRY_BAR=42
//  BAZ=true
//  BARRIES_KEY1_BAR=42
//  QUXXY_QUX=ipsum
//
// Or with prefix:
//  MYAPP_FOO=foo
//  MYAPP_BARRY_BAR=42
//  MYAPP_BAZ=true
//  MYAPP_BARRIES_KEY1_BAR=42
//  MYAPP_QUXXY_QUX=ipsum

func main() {    
    var c config

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

    e.Unmarshal(&c)
}