var upgrader = websocket.Upgrader{
  CheckOrigin: func(r *http.Request) bool { return true }, // 允许跨域
}

func handleWebSocket(w http.ResponseWriter, r *http.Request) {
  conn, err := upgrader.Upgrade(w, r, nil)
  if err != nil {
    log.Println("升级失败:", err)
    return
  }
  defer conn.Close()

  for {
    mt, message, err := conn.ReadMessage()
    if err != nil {
      break
    }
    log.Printf("收到: %s", message)
    // 回显消息
    conn.WriteMessage(mt, []byte("echo: "+string(message)))
  }
}

func main() {
  http.HandleFunc("/ws", handleWebSocket)
  log.Println("服务启动在 :8080")
  log.Fatal(http.ListenAndServe(":8080", nil))
}

func handleWebSocket(w http.ResponseWriter, r *http.Request) {
  conn, err := upgrader.Upgrade(w, r, nil)
  if err != nil {
    log.Println(err)
    return
  }
  defer conn.Close()
  clients[conn] = true

  go func() {
    for {
      _, message, err := conn.ReadMessage()
      if err != nil {
        delete(clients, conn)
        break
      }
      broadcast     }
  }()
}

// 广播协程 func broadcastMessages() {
  for {
    msg :=     for client := range clients {
      err := client.WriteMessage(websocket.TextMessage, msg)
      if err != nil {
        client.Close()
        delete(clients, client)
      }
    }
  }
}