Cannot read properties of undefined (reading 'publish')"

[bobwatcherx]

my code : https://github.com/bobwatcherx/grapapollomain.git
codesanbox : https://codesandbox.io/s/practical-goldwasser-nyy9rw?file=/index.js
PREVIEW APOLLO:https://nyy9rw.sse.codesandbox.io

I'm having problems when I subscribe
on apollo

the error is Cannot read properties of undefined (reading 'publish')"

and when I see an error in the terminal like this
npx [email protected] --endpoint=ws://localhost:4000/graphql
Diagnostics ws://localhost:4000/graphql
️ Connection refused (ECONNREFUSED)
Is the address correct?
Is the server running?

I've followed various tutorials on the internet, including codesanbox from Apollo itself but it doesn't work

if you can give me a simple code example, thanks

[glasser]

This suggests that pubsub in pubsub.publish is undefined. That's because you are trying to make it refer to the top-level const pubsub = but the line hello:async (_,payload,{pubsub})=>{ is definining a function that unpacks its third argument's pubsub field into the local variable pubsub. Deleting ,{pubsub} here and elsewhere may help.