simple websocket example with golang

## index.html
<html>
<head>
    <title>WebSocket demo</title>
</head>
<body>

    <div>
        <form>
            <label for="numberfield">Number</label>
            <input type="text" id="numberfield" placeholder="12"/><br />
            <button type="button" id="sendBtn">Send</button>
        </form>
    </div>
    <div id="container"></div>

    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
    <script type="text/javascript">
        $(function () {
            var ws;

            if (window.WebSocket === undefined) {
                $("#container").append("Your browser does not support WebSockets");
                return;
            } else {
                ws = initWS();
            }

            function initWS() {
                var socket = new WebSocket("ws://localhost:8080/ws"),
                    container = $("#container")
                socket.onopen = function() {
                    container.append("<p>Socket is open</p>");
                };
                socket.onmessage = function (e) {
                    container.append("<p> Got some shit:" + e.data + "</p>");
                }
                socket.onclose = function () {
                    container.append("<p>Socket closed</p>");
                }

                return socket;
            }

            $("#sendBtn").click(function (e) {
                e.preventDefault();
                ws.send(JSON.stringify({ Num: parseInt($("#numberfield").val()) }));
            });
        });
    </script>
</body>
</html>

## ws.go
package main

import (
	"fmt"
	"github.com/gorilla/websocket"
	"io/ioutil"
	"net/http"
)

type msg struct {
	Num int
}

func main() {
	http.HandleFunc("/ws", wsHandler)
	http.HandleFunc("/", rootHandler)

	panic(http.ListenAndServe(":8080", nil))
}

func rootHandler(w http.ResponseWriter, r *http.Request) {
	content, err := ioutil.ReadFile("index.html")
	if err != nil {
		fmt.Println("Could not open file.", err)
	}
	fmt.Fprintf(w, "%s", content)
}

func wsHandler(w http.ResponseWriter, r *http.Request) {
	if r.Header.Get("Origin") != "http://"+r.Host {
		http.Error(w, "Origin not allowed", 403)
		return
	}
	conn, err := websocket.Upgrade(w, r, w.Header(), 1024, 1024)
	if err != nil {
		http.Error(w, "Could not open websocket connection", http.StatusBadRequest)
	}

	go echo(conn)
}

func echo(conn *websocket.Conn) {
	for {
		m := msg{}

		err := conn.ReadJSON(&m)
		if err != nil {
			fmt.Println("Error reading json.", err)
		}

		fmt.Printf("Got message: %#v\n", m)

		if err = conn.WriteJSON(m); err != nil {
			fmt.Println(err)
		}
	}
}