config.go
func LoadWithEnv(conf interface{}, configPaths ...string) error {
	return loadWithFunc(conf, configPaths, envReplacer, yaml.Unmarshal)
}
func LoadWithEnv(conf interface{}, configPaths ...string) error {
	return loadWithFunc(conf, configPaths, envReplacer, yaml.Unmarshal)
}
// LoadWithEnv loads YAML files with Env
// replace {{ env "ENV" }} to os.Getenv("ENV")
// if you set default value then {{ env "ENV" "default" }}