First-stab at a transparent HTTP proxy in Go; a "getting started" project.

proxy.go

package main

import (
        "http"
        "net"
	"io/ioutil"
	"os"
	"fmt"
)

type handler struct{}

func (h *handler) ServeHTTP(resp http.ResponseWriter, req *http.Request) {
  	// Open new TCP connection to the server                                        
	client_tcp_conn, err := net.Dial("tcp", "", req.URL.Host)
        if client_tcp_conn == nil {
	        fmt.Printf("Error: %s\n", err.String())
	        os.Exit(1)
	}
        // Start a new HTTP connection on it                                            
	client_http_conn := http.NewClientConn(client_tcp_conn, nil)
        // Pass on the request                                                          
	client_http_conn.Write(req)
	// Read back the reply                                                          
	client_resp, _ := client_http_conn.Read()
	// Write the reply to the original connection                                   
        reply, _ := ioutil.ReadAll(client_resp.Body)
	resp.Write(reply)
        // Close the connection to the server                                           
	client_http_conn.Close()
}

func main() {
	local, err := net.Listen("tcp", "127.0.0.1:10000")
	if local == nil {
                fmt.Printf("Error: %s\n", err.String())
                os.Exit(1)
        }
        h := new(handler)
        http.Serve(local, h)
}

result.txt

$ curl -sS http://troutwine.us | wc -l
52

$ curl -sS --proxy1.0 127.0.0.1:100000 http://troutwine.us | wc -l
curl: (7) couldn't connect to host