C# Long running Azure function to subscribe to GraphQL

I am looking for some C# test code that I can run as an Azure function to subscribe (not poll) to a GraphQL endpoint and log any messages.

C# to subscribe to GraphQL is easy but running as a long-running Azure function seems harder.

I can add you to a postman account that subscribes to the Graph QL for reference.
Auth for the GraphQL is tokenised. end point URL will be provided.

Needs doing by Sunday latest.