一个简单的Golang实现的HTTP Proxy方法

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package main   import (   "bytes"   "fmt"   "io"   "log"   "net"   "net/url"   "strings" )   func main() {   log.SetFlags(log.LstdFlags|log.Lshortfile)   l, err := net.Listen("tcp", ":8081")   if err != nil {     log.Panic(err)   }     for {     client, err := l.Accept()     if err != nil {       log.Panic(err)     }       go handleClientRequest(client)   } }   func handleClientRequest(client net.Conn) {   if client == nil {     return   }   defer client.Close()     var b [1024]byte   n, err := client.Read(b[:])   if err != nil {     log.Println(err)     return   }   var method, host, address string   fmt.Sscanf(string(b[:bytes.IndexByte(b[:], '\n')]), "%s%s", &method, &host)   hostPortURL, err := url.Parse(host)   if err != nil {     log.Println(err)     return   }     if hostPortURL.Opaque == "443" { //https访问     address = hostPortURL.Scheme + ":443"   } else { //http访问     if strings.Index(hostPortURL.Host, ":") == -1 { //host不带端口， 默认80       address = hostPortURL.Host + ":80"     } else {       address = hostPortURL.Host     }   }     //获得了请求的host和port，就开始拨号吧   server, err := net.Dial("tcp", address)   if err != nil {     log.Println(err)     return   }   if method == "CONNECT" {     fmt.Fprint(client, "HTTP/1.1 200 Connection established\r\n")   } else {     server.Write(b[:n])   }   //进行转发   go io.Copy(server, client)   io.Copy(client, server) }