golang 取得本机出口IP

package main
import (
    "log"
    "net"
)
// Get preferred outbound ip of this machine
func GetOutboundIP() string {
    conn, err := net.Dial("udp", "223.5.5.5:53")
    if err != nil {
        log.Fatal(err)
    }
    defer conn.Close()
    localAddr := conn.LocalAddr().(*net.UDPAddr)
    return localAddr.IP.String()
}
func main() {
    log.SetFlags(log.Lshortfile)
    log.Println(GetOutboundIP()) // main.go:21: 172.31.0.8
}