[转]good sample of Go

from 《Go语言.云动力》
  1 package main
  2 
  3 import (
  4     "io"
  5     "log"
  6     "net/http"
  7     "os"
  8     "os/exec"
  9     "strconv"
 10 )
 11 
 12 var uniq = make(chan int)
 13 
 14 func init() {
 15     go func() {
 16         for i := 0; ; i++ {
 17             uniq <- i
 18         }
 19     }()
 20 }
 21 
 22 func main() {
 23     if err := os.Chdir(os.TempDir()); err != nil {
 24         log.Fatal(err)
 25     }
 26 
 27     http.HandleFunc("/", FrontPage)
 28     http.HandleFunc("/compile", Compile)
 29     log.Fatal(http.ListenAndServe("127.0.0.1:1234", nil))
 30 }
 31 
 32 func FrontPage(w http.ResponseWriter, _ *http.Request) {
 33     w.Write([]byte(frontPage))
 34 }
 35 
 36 func err(w http.ResponseWriter, e error) bool {
 37     if e != nil {
 38         w.Write([]byte(e.Error()))
 39         return true
 40     }
 41     return false
 42 }
 43 
 44 func Compile(w http.ResponseWriter, req *http.Request) {
 45     x := "play_" + strconv.Itoa(<-uniq) + ".go"
 46 
 47     f, e := os.Create(x)
 48     if err(w, e) {
 49         return
 50     }
 51 
 52     defer os.Remove(x)
 53     defer f.Close()
 54 
 55     _, e = io.Copy(f, req.Body)
 56     if err(w, e) {
 57         return
 58     }
 59     f.Close()
 60 
 61     cmd := exec.Command("go", "run", x)
 62     o, e := cmd.CombinedOutput()
 63     if err(w, e) {
 64         return
 65     }
 66 
 67     w.Write(o)
 68 }
 69 
 70 const frontPage = `<!doctype html>
 71 <html><head>
 72 <script>
 73 var req;
 74 function compile(){
 75     var prog = document.getElementById("edit").value;
 76     var req = new XMLHttpRequest ();
 77     req.onreadystatechange = function() {
 78         if (!req || req.readyState != 4)
 79             return;
 80         document.getElementById("output").innerHTML = req.responseText;
 81     }
 82     req.open("POST", "/compile", true);
 83     req.setRequestHeader("Content-Type", "text/plain;charset=utf-8");
 84     req.send(prog);
 85 }
 86 
 87 </script>
 88 </head>
 89 <body>
 90 <textarea rows="25" cols="80" id="edit" spellcheck="false">
 91 
 92 package main
 93 import "fmt"    
 94 func main(){
 95     fmt.Println("hello, world")
 96 }
 97 </textarea>
 98 <button onclick="compile();">run</button>
 99 <div id="output"></div>
100 </body>
101 </html>
102 `