使用go编写一个流量转发程序

以下是一个简单的流量转发程序的示例，使用Go语言编写：

package main

import (
    "fmt"
    "net"
)

func main() {
    listenAddr := "127.0.0.1:8000"
    forwardAddr := "127.0.0.1:9000"

    listener, err := net.Listen("tcp", listenAddr)
    if err != nil {
        fmt.Println("Error listening:", err.Error())
        return
    }
    defer listener.Close()
    fmt.Println("Listening on", listenAddr)

    for {
        conn, err := listener.Accept()
        if err != nil {
            fmt.Println("Error accepting:", err.Error())
            continue
        }
        go handleConnection(conn, forwardAddr)
    }
}

func handleConnection(conn net.Conn, forwardAddr string) {
    forward, err := net.Dial("tcp", forwardAddr)
    if err != nil {
        fmt.Println("Error forwarding:", err.Error())
        conn.Close()
        return
    }
    defer forward.Close()

    go func() {
        _, err := conn.Write([]byte("Connected to forward server\n"))
        if err != nil {
            fmt.Println("Error writing to client:", err.Error())
            forward.Close()
            conn.Close()
            return
        }
    }()

    go func() {
        _, err := forward.Write([]byte("Connected to client\n"))
        if err != nil {
            fmt.Println("Error writing to forward server:", err.Error())
            forward.Close()
            conn.Close()
            return
        }
    }()

    buffer := make([]byte, 1024)
    for {
        n, err := conn.Read(buffer)
        if err != nil {
            fmt.Println("Error reading from client:", err.Error())
            forward.Close()
            conn.Close()
            return
        }
        _, err = forward.Write(buffer[:n])
        if err != nil {
            fmt.Println("Error writing to forward server:", err.Error())
            forward.Close()
            conn.Close()
            return
        }
    }
}

该程序监听在本地地址的8000端口上，并将连接转发到本地地址的9000端口上。它使用两个goroutine，一个处理从客户端读取的数据并将其转发到服务器，另一个处理从服务器读取的数据并将其转发到客户端。在处理连接时，该程序还向客户端和服务器发送了一些欢迎信息