Async tasks work in now dev but break in production.
Run now dev, then open http://localhost:3000/api/test. You'll see an OK on the page, and the now dev process should log:
Beginning asyncTask...
asyncTask complete
Run now, then open the resulting /api/test route. You'll see the OK, but the logs will indicate that the task never completed:
START RequestId: [id] Version: $LATEST
2019-09-30T16:45:48.655Z [id] INFO Beginning asyncTask...
END RequestId: [id]
REPORT RequestId: [id] Duration: 49.42 ms Billed Duration: 100 ms Memory Size: 3008 MB Max Memory Used: 85 MB Init Duration: 180.44 ms