code: func (d *destination) String() string {
  	if d.service.fwm != 0 {
  		return fmt.Sprintf("%v", d.ip)
  	}
  	ip := d.ip.String()
  	port := strconv.Itoa(int(d.service.port))
  	return fmt.Sprintf("%v/%v", net.JoinHostPort(ip, port), d.service.proto)
  }
docs: // String returns a string representing a destination.