message: fix(server): fix panic in Connection::graceful_shutdown
diff: @@ -502,14 +502,21 @@ where
  ///
  /// This `Connection` should continue to be polled until shutdown
  /// can finish.
  + ///
  + /// # Note
  + ///
  + /// This should only be called while the `Connection` future is still
  + /// pending. If called after `Connection::poll` has resolved, this does
  + /// nothing.
  pub fn graceful_shutdown(self: Pin<&mut Self>) {
  - match self.project().conn.as_mut().unwrap() {
  - ProtoServer::H1(ref mut h1) => {
  + match self.project().conn {
  + Some(ProtoServer::H1(ref mut h1)) => {
  h1.disable_keep_alive();
  }
  - ProtoServer::H2(ref mut h2) => {
  + Some(ProtoServer::H2(ref mut h2)) => {
  h2.graceful_shutdown();
  }
  + None => (),
  }
  }
  