netaddress.go
func (na *NetAddress) String() string {
	if na.str == "" {
		na.str = net.JoinHostPort(
			na.IP.String(),
			strconv.FormatUint(uint64(na.Port), 10),
		)
	}
	return na.str
}
func (na *NetAddress) String() string {
	if na.str == "" {
		na.str = net.JoinHostPort(
			na.IP.String(),
			strconv.FormatUint(uint64(na.Port), 10),
		)
	}
	return na.str
}
// String representation.