Reproduction for net/http: Response.Write has bogus Connection header after auto-ungzipped Content-Length response

main.go

package main

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

// A reproduction of a bug where http.transport.RoundTrip returns an http.Response
// that contains both "Connection: close" and "Connection: keep-alive" headers.

// Pass in a file with the response to parse as the first argument.

func main() {

	// Minimal response to reproduce the bug. Content is a gzipped UTF-8 "FOO".
	response, _ := ioutil.ReadFile(os.Args[1])

	ln, err := net.Listen("tcp", ":8080")
	if err != nil {
		// handle error
	}
	go func() {
		for {
			conn, err := ln.Accept()
			if err != nil {
				// handle error
			}
			conn.Write(response)
		}
	}()
	t := &http.Transport{}
	req, _ := http.NewRequest("GET", "http://localhost:8080", nil)
	res, rt_err := t.RoundTrip(req)
	if rt_err != nil {
		log.Fatalf("ERROR RT: %v\n", rt_err)
	}
	buf, err := httputil.DumpResponse(res, false)
	if err != nil {
		log.Fatalf("ERROR DR: %v\n", err)
	}
	fmt.Printf("http.Transport.RoundTrip response: %s\n", buf)

	res, rt_err = http.DefaultClient.Do(req)
	if rt_err != nil {
		log.Fatalf("ERROR RT: %v\n", rt_err)
	}
	buf, err = httputil.DumpResponse(res, false)
	if err != nil {
		log.Fatalf("ERROR DR: %v\n", err)
	}
	fmt.Printf("http.DefaultClient.Do Response: %s\n", buf)
}

valid_gzipped_response.txt

HTTP/1.1 200 OK
Content-Encoding: gzip
Content-Length: 23
Connection: keep-alive
Keep-Alive: timeout=7200

\8B\00\00\00\00\00\00\00s\F3\F7\00\AB'\D4\00\00\00