message: prevent socket from hanging when the connection ends
diff: @@ -37,6 +37,8 @@ export default (async function startServer(
  const messageReader = new SocketMessageReader(socket);
  const messageWriter = new SocketMessageWriter(socket);
  + socket.on('close', () => process.exit(0));
  +
  messageReader.listen(message => {
  try {
  if (message.id != null) {
  