如何从golang的websocket服务器向客户端主动发送消息

尝试打包websocket。

这是Godoc的一个简单示例：

var upgrader = websocket.Upgrader{    ReadBufferSize:  1024,    WriteBufferSize: 1024,}func handler(w http.ResponseWriter, r *http.Request) {    conn, err := upgrader.Upgrade(w, r, nil)    if err != nil {        log.Println(err)        return    }    defer conn.Close()    msg := []byte("Let's start to talk something.")    err = conn.WriteMessage(websocket.TextMessage, msg)    if err != nil {        log.Println(err)    }    // do other stuff...}