Unsubscribe lock issue fixes

appsync_ws_client/client.py

@@ -21,7 +21,7 @@ def __init__(self, url: str, auth_function: Callable[[], Dict[str, str]], max_re
         self._acknowledged_event = threading.Event()
         self.max_retries = max_retries
         self.retry_count = 0
-        self.lock = threading.Lock()
+        self.lock = threading.RLock()
 
     def _build_ws_url(self) -> str:
         """