Minimal go server with logging and all the headers visible.

ms.go

package main

/**
* Minimal go server with logging and all the headers visible.
*
* To build it simply
* '$go build ms.go'
*
* # To lear how to use it simply:
* $ ms --help
* Usage of ms:
*   -dir string
*         dir to serve the content (default "src")
*   -port string
*         server listen address (default ":8080")
* # This command  will start a server in the 8080 and serve content from src dir
* $ms
* # This will start in port 8181 and dir public
* $ms --port :8181 --dir public
*
 */
import (
	"flag"
	"fmt"
	"log"
	"net/http"
	"os"
	"strings"
	"time"
)

type key int

var (
	listenAddr string
	healthy    int32
)

func main() {
	// This is to manage parameters or flags for the program
	var port, dir string
	flag.StringVar(&port, "port", ":8080", "server listen address")
	flag.StringVar(&dir, "dir", "src", "dir to serve the content")
	flag.Parse()
	// This is the line to configure the logger, simply to print in the console
	logger := log.New(os.Stdout, "http: ", log.LstdFlags)
	logger.Println("Server is starting...")

	router := http.NewServeMux()
	router.Handle("/", http.FileServer(http.Dir(dir)))

	server := &http.Server{
		Addr:         port,
		Handler:      logging(logger)(router),
		ErrorLog:     logger,
		ReadTimeout:  5 * time.Second, // Allways is better to have TO
		WriteTimeout: 10 * time.Second,
		IdleTimeout:  15 * time.Second,
	}

	logger.Fatal(server.ListenAndServe())

}

// Manages the logger and adds an anonymous function to wrap the handler
func logging(logger *log.Logger) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			defer func() {
				logger.Println(r.Method, r.URL.Path, r.RemoteAddr, r.UserAgent(), "\n")
				logger.Println(formatRequest(r))
			}()
			next.ServeHTTP(w, r)
		})
	}
}

// formatRequest shows all the headers of a request
func formatRequest(r *http.Request) string {
	// Create return string
	var request []string
	// Add the request string
	url := fmt.Sprintf("%v %v %v", r.Method, r.URL, r.Proto)
	request = append(request, url)
	// Add the host
	request = append(request, fmt.Sprintf("Host: %v", r.Host))
	// Loop through headers
	for name, headers := range r.Header {
		name = strings.ToLower(name)
		for _, h := range headers {
			request = append(request, fmt.Sprintf("%v: %v", name, h))
		}
	}

	// If this is a POST, add post data
	if r.Method == "POST" {
		r.ParseForm()
		request = append(request, "\n")
		request = append(request, r.Form.Encode())
	}
	// Return the request as a string
	return strings.Join(request, "\n")
}