code: func (a AddrSpec) Address() string {
  	if 0 != len(a.IP) {
  		return net.JoinHostPort(a.IP.String(), strconv.Itoa(a.Port))
  	}
  	return net.JoinHostPort(a.FQDN, strconv.Itoa(a.Port))
  }
docs: // Address returns a string suitable to dial; prefer returning IP-based
  // address, fallback to FQDN