code: func Localhost() (net.IP, error) {
  	if ip := localhostLookup(); ip != nil {
  		return ip, nil
  	}
  	if ip := loopbackIP(); ip != nil {
  		return ip, nil
  	}
  	return nil, errors.New("no loopback ip found")
  }
docs: // Localhost returns the first address found when
  // doing a lookup of "localhost". If not successful,
  // it looks for an ip on the loopback interfaces.