一个golang http包自带的绝佳示例

package main

import (
	"bytes"
	"expvar"
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"os/exec"
	"strconv"
	"sync"
)

// hello world, the web server
var helloRequests = expvar.NewInt("hello-requests")

func HelloServer(w http.ResponseWriter, req *http.Request) {
	helloRequests.Add(1)
	io.WriteString(w, "hello, world!\n")
}

// Simple counter server. POSTing to it will set the value.
type Counter struct {
	mu sync.Mutex // protects n
	n  int
}

// This makes Counter satisfy the expvar.Var interface, so we can export
// it directly.
func (ctr *Counter) String() string {
	ctr.mu.Lock()
	defer ctr.mu.Unlock()
	return fmt.Sprintf("%d", ctr.n)
}

func (ctr *Counter) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	ctr.mu.Lock()
	defer ctr.mu.Unlock()
	switch req.Method {
	case "GET":
		ctr.n++
	case "POST":
		buf := new(bytes.Buffer)
		io.Copy(buf, req.Body)
		body := buf.String()
		if n, err := strconv.Atoi(body); err != nil {
			fmt.Fprintf(w, "bad POST: %v\nbody: [%v]\n", err, body)
		} else {
			ctr.n = n
			fmt.Fprint(w, "counter reset\n")
		}
	}
	fmt.Fprintf(w, "counter = %d\n", ctr.n)
}

// simple flag server
var booleanflag = flag.Bool("boolean", true, "another flag for testing")

func FlagServer(w http.ResponseWriter, req *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	fmt.Fprint(w, "Flags:\n")
	flag.VisitAll(func(f *flag.Flag) {
		if f.Value.String() != f.DefValue {
			fmt.Fprintf(w, "%s = %s [default = %s]\n", f.Name, f.Value.String(), f.DefValue)
		} else {
			fmt.Fprintf(w, "%s = %s\n", f.Name, f.Value.String())
		}
	})
}

// simple argument server
func ArgServer(w http.ResponseWriter, req *http.Request) {
	for _, s := range os.Args {
		fmt.Fprint(w, s, " ")
	}
}

// a channel (just for the fun of it)
type Chan chan int

func ChanCreate() Chan {
	c := make(Chan)
	go func(c Chan) {
		for x := 0; ; x++ {
			c <- x
		}
	}(c)
	return c
}

func (ch Chan) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	io.WriteString(w, fmt.Sprintf("channel send #%d\n", <-ch))
}

// exec a program, redirecting output
func DateServer(rw http.ResponseWriter, req *http.Request) {
	rw.Header().Set("Content-Type", "text/plain; charset=utf-8")

	date, err := exec.Command("/bin/date").Output()
	if err != nil {
		http.Error(rw, err.Error(), 500)
		return
	}
	rw.Write(date)
}

func Logger(w http.ResponseWriter, req *http.Request) {
	log.Print(req.URL)
	http.Error(w, "oops", 404)
}

var webroot = flag.String("root", os.Getenv("HOME"), "web root directory")

func main() {
	flag.Parse()

	// The counter is published as a variable directly.
	ctr := new(Counter)
	expvar.Publish("counter", ctr)
	http.Handle("/counter", ctr)
	http.Handle("/", http.HandlerFunc(Logger))
	http.Handle("/go/", http.StripPrefix("/go/", http.FileServer(http.Dir(*webroot))))
	http.Handle("/chan", ChanCreate())
	http.HandleFunc("/flags", FlagServer)
	http.HandleFunc("/args", ArgServer)
	http.HandleFunc("/go/hello", HelloServer)
	http.HandleFunc("/date", DateServer)
	err := http.ListenAndServe(":12345", nil)
	if err != nil {
		log.Panicln("ListenAndServe:", err)
	}
}

curl http://localhost:12345/counter

curl http://localhost:12345/

curl http://localhost:12345/go

curl http://localhost:12345/chan

curl http://localhost:12345/flags

curl http://localhost:12345/args

curl http://localhost:12345/go/hello

curl http://localhost:12345/date

curl http://localhost:12345/xx

有疑问加站长微信联系（非本文作者）