使用go语言创建HTTP(s)代理100行代码

package main
import (
    "crypto/tls"
    "flag"
    "io"
    "log"
    "net"
    "net/http"
    "time"
)
func handleTunneling(w http.ResponseWriter, r *http.Request) {
	//设置超时防止大量超时导致服务器资源不大量占用
    dest_conn, err := net.DialTimeout("tcp", r.Host, 10*time.Second)
    if err != nil {
        http.Error(w, err.Error(), http.StatusServiceUnavailable)
        return
    }
    w.WriteHeader(http.StatusOK)
    //类型转换
    hijacker, ok := w.(http.Hijacker)
    if !ok {
        http.Error(w, "Hijacking not supported", http.StatusInternalServerError)
        return
    }
    //接管连接
    client_conn, _, err := hijacker.Hijack()
    if err != nil {
        http.Error(w, err.Error(), http.StatusServiceUnavailable)
    }
    go transfer(dest_conn, client_conn)
    go transfer(client_conn, dest_conn)
}
//转发连接的数据
func transfer(destination io.WriteCloser, source io.ReadCloser) {
    defer destination.Close()
    defer source.Close()
    io.Copy(destination, source)
}
func handleHTTP(w http.ResponseWriter, req *http.Request) {
	//roudtrip 传递发送的请求返回响应的结果
    resp, err := http.DefaultTransport.RoundTrip(req)
    if err != nil {
        http.Error(w, err.Error(), http.StatusServiceUnavailable)
        return
    }
    defer resp.Body.Close()
    //把目标服务器的响应header复制
    copyHeader(w.Header(), resp.Header)
    w.WriteHeader(resp.StatusCode)
    io.Copy(w, resp.Body)
}
//复制响应头
func copyHeader(dst, src http.Header) {
    for k, vv := range src {
        for _, v := range vv {
            dst.Add(k, v)
        }
    }
}
func main() {
	//证书路径
    var pemPath string
    flag.StringVar(&pemPath, "pem", "server.pem", "path to pem file")
    //私钥路径
    var keyPath string
    flag.StringVar(&keyPath, "key", "server.key", "path to key file")
    //协议
    var proto string
    flag.StringVar(&proto, "proto", "https", "Proxy protocol (http or https)")
    flag.Parse()
    //只支持http和https协议
    if proto != "http" && proto != "https" {
        log.Fatal("Protocol must be either http or https")
    }
    server := &http.Server{
        Addr: ":8888",
        Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            if r.Method == http.MethodConnect {
            	//支持https websocket deng ... tcp
                handleTunneling(w, r)
            } else {
            	//直接http代理
                handleHTTP(w, r)
            }
        }),
        // 关闭http2
        TLSNextProto: make(map[string]func(*http.Server, *tls.Conn, http.Handler)),
    }
    if proto == "http" {
        log.Fatal(server.ListenAndServe())
    } else {
        log.Fatal(server.ListenAndServeTLS(pemPath, keyPath))
    }
}

http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    if r.Method == http.MethodConnect {
        handleTunneling(w, r)
    } else {
        handleHTTP(w, r)
    }
})

dest_conn, err := net.DialTimeout("tcp", r.Host, 10*time.Second)
if err != nil {
    http.Error(w, err.Error(), http.StatusServiceUnavailable)
    return
 }
 w.WriteHeader(http.StatusOK)

hijacker, ok := w.(http.Hijacker)
    if !ok {
        http.Error(w, "Hijacking not supported", http.StatusInternalServerError)
        return
    }
    client_conn, _, err := hijacker.Hijack()
    if err != nil {
        http.Error(w, err.Error(), http.StatusServiceUnavailable)
    }

go transfer(dest_conn, client_conn)
go transfer(client_conn, dest_conn)

package main
import (
    "crypto/tls"
    "fmt"
    "net/http"
    "net/http/httputil"
    "net/url"
)
func main() {
    u, err := url.Parse("https://localhost:8888")
    if err != nil {
        panic(err)
    }
    tr := &http.Transport{
        Proxy: http.ProxyURL(u),
        // Disable HTTP/2.
        TLSNextProto: make(map[string]func(authority string, c *tls.Conn) http.RoundTripper),
    }
    client := &http.Client{Transport: tr}
    resp, err := client.Get("https://google.com")
    if err != nil {
        panic(err)
    }
    defer resp.Body.Close()
    dump, err := httputil.DumpResponse(resp, true)
    if err != nil {
        panic(err)
    }
    fmt.Printf("%q", dump)
}