//獲取ip
func externalIP() (net.IP, error) {
	ifaces, err := net.Interfaces()
	if err != nil {
		return nil, err
	}
	for _, iface := range ifaces {
		if iface.Flags&net.FlagUp == 0 {
			continue // interface down
		}
		if iface.Flags&net.FlagLoopback != 0 {
			continue // loopback interface
		}
		addrs, err := iface.Addrs()
		if err != nil {
			return nil, err
		}
		for _, addr := range addrs {
			ip := getIpFromAddr(addr)
			if ip == nil {
				continue
			}
			return ip, nil
		}
	}
	return nil, errors.New("connected to the network?")
}
//獲取ip
func getIpFromAddr(addr net.Addr) net.IP {
	var ip net.IP
	switch v := addr.(type) {
	case *net.IPNet:
		ip = v.IP
	case *net.IPAddr:
		ip = v.IP
	}
	if ip == nil || ip.IsLoopback() {
		return nil
	}
	ip = ip.To4()
	if ip == nil {
		return nil // not an ipv4 address
	}
	return ip
}

func main() {
	ip, err := externalIP()
	if err != nil {
		fmt.Println(err)
	}
	fmt.Printf(ip.String())
}

 func GetLocalMac() (mac string) {
	// 獲取本機(jī)的MAC地址
	interfaces, err := net.Interfaces()
 	if err != nil {
		panic("Poor soul, here is what you got: " + err.Error())
 	}
	for _, inter := range interfaces {
 		fmt.Println(inter.Name)
 		mac := inter.HardwareAddr //獲取本機(jī)MAC地址
 		fmt.Println("MAC ===== ", mac)
 	}
 	fmt.Println("MAC = ", mac)
	return mac
}

 //獲取本機(jī)ip地址
 func GetIps() (ips []string) {
 	interfaceAddr, err := net.InterfaceAddrs()
 	if err != nil {
 		fmt.Printf("fail to get net interfaces ipAddress: %v\n", err)
 		return ips
 	}
 	for _, address := range interfaceAddr {
 		ipNet, isVailIpNet := address.(*net.IPNet)
 		if isVailIpNet && !ipNet.IP.IsLoopback() {
 			if ipNet.IP.To4() != nil {
 				ips = append(ips, ipNet.IP.String())
 			}
		}
	}
	fmt.Println("ips = ", ips)
	return ips
 }