envconfig.go
func MustProcess(prefix string, spec interface{}) {
	if err := Process(prefix, spec); err != nil {
		panic(err)
	}
}
func MustProcess(prefix string, spec interface{}) {
	if err := Process(prefix, spec); err != nil {
		panic(err)
	}
}
// MustProcess is the same as Process but panics if an error occurs