package main

import (
        "fmt"
        "net"
        "os"
)

func main() {
        localAddr := net.ParseIP(os.Args[1])
        remoteAddr := net.ParseIP(os.Args[2])
        netProto := os.Args[3]

        c, err := net.DialIP(netProto, &net.IPAddr{localAddr}, &net.IPAddr{remoteAddr})
        if err != nil {
                fmt.Printf("DialIP failed: %v\n", err)
                return
        }
        fmt.Printf("LocalAddr: %v, RemoteAddr: %v\n", c.LocalAddr(), c.RemoteAddr())
}

# ./test 172.23.124.29 172.23.124.30 ip:tcp
LocalAddr: 172.23.124.29, RemoteAddr: <nil>
# ./test 172.23.124.29 172.23.124.30 ip:udp
LocalAddr: 172.23.124.29, RemoteAddr: <nil>
# ./test 172.23.124.29 172.23.124.30 ip:112
LocalAddr: 172.23.124.29, RemoteAddr: <nil>

because 

# strace ./test 172.23.124.29 172.23.124.30 ip:udp

socket(PF_INET, SOCK_RAW, IPPROTO_UDP)  = 3
fcntl(3, F_SETFD, FD_CLOEXEC)           = 0
setsockopt(3, SOL_SOCKET, SO_BROADCAST, [1], 4) = 0
bind(3, {sa_family=AF_INET, sin_port=htons(0),
sin_addr=inet_addr("172.23.124.29")}, 16) = 0
fcntl(3, F_GETFL)                       = 0x2 (flags O_RDWR)
fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK)    = 0
connect(3, {sa_family=AF_INET, sin_port=htons(0),
sin_addr=inet_addr("172.23.124.30")}, 16) = 0
getsockname(3, {sa_family=AF_INET, sin_port=htons(17),
sin_addr=inet_addr("172.23.124.29")}, [16]) = 0
getpeername(3, 0xf8400000e0, [112])     = -1 ENOTCONN (Transport
endpoint is not connected)
======================