class Playwright::WebSocketTransport

def stop
  return unless @ws
  future = Concurrent::Promises.resolvable_future
  @ws.on_close do
    future.fulfill(nil)
  end
  begin
    @ws.close
  rescue EOFError => err
    # ignore EOLError. The connection is already closed.
    future.fulfill(err)
  end
  # Wait for closed actually.
  future.value!(2)
end