feat: Attempted implemented graceful shutdown

[jjm340]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕

Note: If you are opening a pull request against a legacy branch, PLEASE BE AWARE that we generally won't accept these except for things like important security fixes, and only for a limited time.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[feywind]

@jjm340 Thanks for opening a PR. I think I can see some ways we can simplify this, but my main concern is that it might be considered a breaking change. I'd say "let me talk to the team on Thursday" except it's going to be US Thanksgiving :) so many of them will be out. Anyhow, I'll get back to you.

[jjm340]

@jjm340 Thanks for opening a PR. I think I can see some ways we can simplify this, but my main concern is that it might be considered a breaking change. I'd say "let me talk to the team on Thursday" except it's going to be US Thanksgiving :) so many of them will be out. Anyhow, I'll get back to you.

@feywind Thanks!! I had the same thought about this being a breaking change and a colleague and I discussed putting this behind an option flag, but wanted feedback from Google on that. I believe one side effect is that if this approach is used and a message is neither ACKed or NACKed, then the promise would never resolve and keep the consumer open indefinitely.

[feywind]

I'll probably be picking this up again soon - the delay was because there was a fair amount of discussion about the way this should be implemented, and that is wrapping up now.