Heartbeat errors are not propagated / catched

[michaelwittig]

Describe the bug
If the call to changeVisabilityTimeout fails, the Promise is rejected but no one notices. Node.js complains about this with an

UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)

To Reproduce
Steps to reproduce the behaviour:

1. I was running into this because of a missing IAM permission Fix documented required IAM actions #274 and I think that is the easiest way to reproduce the issue

Expected behaviour
I'm not sure but it could be an error event?

I'm willing to provide a fix if we can agree on what's expected.

[rafael-pb]

I believe I had a similar issue in my application. The stack trace didn't help, but my application got killed due to unhandled exception/rejection (my app is configured to die if such thing happen). The reason was changeMessageVisibility call that failed.

By inspecting the code of sqs-consumer, I believe the reason is that inside the methods changeVisabilityTimeoutBatch and changeVisabilityTimeout they do not "await" the promise; therefore the try {} catch {} does not catch the error. It also happens because those who call it do not catch any errors (one is inside a timer and the other is inside a catch block).

I believe adding the await should fix the issue.

[michaelwittig]

the issue is fixed. Thanks @rafael-pb