* Fixed tasks cancellation on app shutdown

chain_service/app.py

@@ -25,12 +25,13 @@ async def startup_event():
 @application.on_event("shutdown")
 async def shutdown_event():
     async with application.state.tasks_lock:
-        for task in application.state.tasks.values():
-            try:
-                task.cancel()
-            except asyncio.CancelledError:
-                pass
-        await asyncio.gather(*application.state.tasks.values(), return_exceptions=True)
+        for task_list in application.state.tasks.values():
+            for task in task_list:
+                try:
+                    task.cancel()
+                except asyncio.CancelledError:
+                    pass
+
         application.state.tasks.clear()