fix: do a best-effort transmit on connection close

If we're shutting down ungracefully, we can make a best-effort attempt
to write the CONNECTION_CLOSE to the socket and notify the peer. If
we're in the middle of graceful shutdown, it doesn't hurt, either.

Author: colinmarc

noq/src/connection.rs

@@ -1709,6 +1709,14 @@ impl State {
     fn close(&mut self, error_code: VarInt, reason: Bytes, shared: &Shared) {
         self.inner.close(self.runtime.now(), error_code, reason);
         self.terminate(ConnectionError::LocallyClosed, shared);
+
+        // If we're able to synchronously write the CONNECTION_CLOSED, it's
+        // advantageous to do so; we might be shutting down ungracefully, and
+        // this way we have a decent shot of notifying the peer.
+        let waker = std::task::Waker::noop();
+        let mut cx = std::task::Context::from_waker(waker);
+        let _ = self.drive_transmit(&mut cx);
+
         self.wake();
     }