update 03.3md with proper code block syntax

en/03.3.md

@@ -34,36 +34,38 @@ In the previous section we saw that Go uses `ListenAndServe` to handle these ste
 
 Let's take a look at the `http` package's source code.
 
-	//Build version go1.1.2.
-	func (srv *Server) Serve(l net.Listener) error {
-		defer l.Close()
-		var tempDelay time.Duration // how long to sleep on accept failure
-		for {
-			rw, e := l.Accept()
-			if e != nil {
-				if ne, ok := e.(net.Error); ok && ne.Temporary() {
-					if tempDelay == 0 {
-						tempDelay = 5 * time.Millisecond
-					} else {
-						tempDelay *= 2
-					}
-					if max := 1 * time.Second; tempDelay > max {
-						tempDelay = max
-					}
-					log.Printf("http: Accept error: %v; retrying in %v", e, tempDelay)
-					time.Sleep(tempDelay)
-					continue
+```go
+//Build version go1.1.2.
+func (srv *Server) Serve(l net.Listener) error {
+	defer l.Close()
+	var tempDelay time.Duration // how long to sleep on accept failure
+	for {
+		rw, e := l.Accept()
+		if e != nil {
+			if ne, ok := e.(net.Error); ok && ne.Temporary() {
+				if tempDelay == 0 {
+					tempDelay = 5 * time.Millisecond
+				} else {
+					tempDelay *= 2
 				}
-				return e
-			}
-			tempDelay = 0
-			c, err := srv.newConn(rw)
-			if err != nil {
+				if max := 1 * time.Second; tempDelay > max {
+					tempDelay = max
+				}
+				log.Printf("http: Accept error: %v; retrying in %v", e, tempDelay)
+				time.Sleep(tempDelay)
 				continue
 			}
-			go c.serve()
+			return e
 		}
+		tempDelay = 0
+		c, err := srv.newConn(rw)
+		if err != nil {
+			continue
+		}
+		go c.serve()
 	}
+}
+```
 
 	
 How do we accept client requests after we begin listening to a port? In the source code, we can see that `srv.Serve(net.Listener)` is called to handle client requests. In the body of the function there is a `for{}`. It accepts a request, creates a new connection then starts a new goroutine, passing the request data to the `go c.serve()` goroutine. This is how Go supports high concurrency, and every goroutine is independent.