feat: add option of specifying resolveMode

[brettstack]

Allows resolving using Promise, callback, or the default context.succeed.

API decisions were made to support backwards compatibility. We will clean up the interface in a future major version bump

exports.handler = async (event, context) => awsServerlessExpress.proxy(server, event, context, 'PROMISE').promise

Please ensure all pull requests are made against the develop branch.

Issue #134, if available:

Description of changes:

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[keetonian]

Would it be possible to add in a test with an async handler like was given in #134 ? It seems like that was the reason behind this code change; it would be nice to see a test that explicitly checks against that use case. Let me know if you already do test this- I can see some references to promise in your tests which might cover it; I don't know enough javascript yet to be able to tell.

[brettstack]

Covered here https://github.com/awslabs/aws-serverless-express/pull/173/files#diff-971abd8c6c8db00bc212414ea19e1807R183. Async is syntactic sugar for Promise. Can't use async in the test as it will fail in our test runs for earlier versions of Node.js

[keetonian]

Ok, thank you for the clarification!

[zoellner]

Looks like this feature is missing from the documentation.

[adrai]

@brettstack what is the current suggested way to call the proxy function? like in the readme (no callback, only context)? or with callback and how?

[brettstack]

Open to PRs updating the docs. I haven't performed a performance benchmark on context.succeed vs Promise resolution which is the main reason I didn't change the example

[zoellner]

Added a PR for the docs: #212