Cloud Function with Pub/sub trigger creates new Eventarc subscription for the Topic

[Shubham0051]

I'm currently working on a project where I'm using Google Cloud Functions triggered by Pub/Sub messages. In my workflow, When I create a Cloud Function with pubsub trigger, it automatically create a new eventarc subscription in Google Cloud Pub/Sub Topic. 

I'm looking for a way to have a Cloud Function ask for a subscription in Pub/Sub during configuration .

I've searched through the Google Cloud Functions documentation and experimented with various things but it seems there's no built-in feature that allows Cloud Function to  be attached to the existing subscription.