[ASK] How to use broadcast server API about koa-websocket HOT 2 OPEN

app.ws.use((ctx) => {

  /*
   * `ctx` is the regular koa context created from the `ws`
   * onConnection `socket.upgradeReq` object.
   */
  ctx.websocket.broadcast = function(data) {
    app.ws.server.clients.forEach(function each(client) {
      client.send(data);
    });
  };

  // the websocket is added to the context on `ctx.websocket`.
  ctx.websocket.on('message', function(message) {
    // do something with the message from client
    ctx.websocket.broadcast('something');
  });
});