fix: ws server terminate subscriptions when connection is closed by the client.

tests/tests/integration_tests.rs

@@ -334,5 +334,5 @@ async fn ws_server_should_stop_subscription_after_client_drop() {
 	assert_eq!(res.as_ref(), Some(&1));
 	drop(client);
 	// assert that the server received `SubscriptionClosed` after the client was dropped.
-	assert!(rx.next().await.is_some());
+	assert!(matches!(rx.next().await.unwrap(), SubscriptionClosedError(_)));
 }

ws-client/src/client.rs

@@ -678,6 +678,6 @@ async fn background_task(
 		}
 	}
 
-	// Send WebSocket close reason to the server (this might fail if the server already terminated the connection).
+	// Send close message to the server.
 	let _ = sender.close().await;
 }