Ignore cancellederror when closing connections

Author: SmileyChris

graphql_ws/base_async.py

@@ -159,7 +159,10 @@ async def on_close(self, connection_context):
             for op_id in connection_context.operations
         ) + tuple(task.cancel() for task in connection_context.pending_tasks)
         if awaitables:
-            await asyncio.gather(*awaitables, loop=self.loop)
+            try:
+                await asyncio.gather(*awaitables, loop=self.loop)
+            except asyncio.CancelledError:
+                pass
 
     async def on_stop(self, connection_context, op_id):
         await self.unsubscribe(connection_context, op_id)