fix async error

app.py

@@ -213,17 +213,18 @@ async def main(message: cl.Message):
     try:
         lcel_rag_chain = cl.user_session.get("lcel_rag_chain")
 
-        msg = cl.Message(content="")
-
-        chunks = await cl.make_async(lcel_rag_chain.stream)(
+        # Get the response as a single string
+        response = await cl.make_async(lcel_rag_chain.invoke)(
             {"query": message.content},
             config=RunnableConfig(callbacks=[cl.LangchainCallbackHandler()]),
         )
         
-        async for chunk in chunks:
-            await msg.stream_token(chunk)
+        # Create and send the message with the response
+        await cl.Message(
+            content=response,
+            author="Paul Graham Essay Bot"
+        ).send()
 
-        await msg.send()
     except Exception as e:
         error_message = str(e)
         if "Connection reset by peer" in error_message or "Connection aborted" in error_message: