func read(ctx context.Context, c *websocket.Conn) ([]byte, error) {
	ctx, cancel := context.WithTimeout(ctx, time.Minute*30)
	defer cancel()

	_, r, err := c.Reader(ctx)
	if err != nil {
		return nil, err
	}

	// One minute max to read the received message.
	time.AfterFunc(time.Minute, cancel)

	return ioutil.ReadAll(r)
}