echoDump can bind to any hostname and port, and responds to all accepted queries by echoing a dump of the incoming request.

echoDump.go

// echoDump is a minimal "echo" server that responds with a dump of the incoming request.
// (Based on https://github.com/adonovan/gopl.io/blob/master/ch1/server1/main.go)
package main

import (
	"flag"
	"fmt"
	"log"
	"net/http"
	"net/http/httputil"
)

var site string // the host and port we'll listen on
func init() {
	flag.StringVar(&site, "site", ":8000", "host:port value") // pick up commandline site, or default
}

func main() {
	flag.Parse()
	http.HandleFunc("/", handler)           // each request calls handler
	fmt.Println("Listening on site:", site) // let user know what we've bound to
	log.Fatal(http.ListenAndServe(site, nil))
}

// handler echoes a dump of the incoming request/
func handler(w http.ResponseWriter, r *http.Request) {

	dump, err := httputil.DumpRequest(r, true)
	if err != nil {
		fmt.Printf("DumpRequest generated err: %q\n", err)
		http.Error(w, fmt.Sprint(err), http.StatusInternalServerError)
		return
	}

	fmt.Printf("Request:\n%s\n", dump)
	fmt.Fprintf(w, "Request:\n%s\n", dump)
}