Basic Go TCP proxy...borrowed from someone...

proxy.go

package main

import (
  "net"
	"fmt"
	"io"
	"os"
	"crypto/sha1"
	"time"
)

func main() {
	now := time.Now().Unix()
	nowstr := fmt.Sprintf("%d", now)
	h := sha1.New()
	h.Write([]byte(nowstr))
	fmt.Printf("%v\n", h.Sum(nil));

	if len(os.Args) != 3 {
		fatal("usage: netfwd local remote")
	}

	localAddr := os.Args[1]
	remoteAddr := os.Args[2]

	local, err := net.Listen("tcp", localAddr)
	if local == nil {
		fatal("Cannot listen: %v", err)
	}

	for {
		conn, err := local.Accept()
		if conn == nil {
			fatal("accept failed: %v", err)
		}
		go forward(conn, remoteAddr)
	}
}

func forward(local net.Conn, remoteAddr string) {
	remote, err := net.Dial("tcp", remoteAddr)
	if remote == nil {
		fmt.Fprintf(os.Stderr, "remote dial failed: %v\n", err)
	}

	go io.Copy(local, remote)
	go io.Copy(remote, local)
}

func fatal(s string, a ... interface{}) {
	fmt.Fprintf(os.Stderr, "netfdw: %s \n", fmt.Sprintf(s, a))
	os.Exit(2)
}