Feature Request: Update to Pubsub v2

This example is awesome! I really appreciate you putting it together! However, it would be better if you could clean it up a bit and migrate it to the cloud.google.com/go/pubsub/v2 libraries following the https://github.com/googleapis/google-cloud-go/blob/main/pubsub/MIGRATING.md document.

(Also, are you aware of an automated tool that might do a first pass at this? Some sort of codemod would be _extremely_ welcome as this is pretty tedious!)