`context.callbackWaitsForEmptyEventLoop` is a `var`, actually

This is a very interesting example on https://docs.aws.amazon.com/lambda/latest/dg/nodejs-handler.html.

In the following example, the response from Amazon S3 is returned to the invoker as soon as it's available. The timeout running on the event loop is frozen, and it continues running the next time the function is invoked.

const AWS = require('aws-sdk')
const s3 = new AWS.S3()

exports.handler = function(event, context, callback) {
  context.callbackWaitsForEmptyEventLoop = false
  s3.listBuckets(null, callback)
  setTimeout(function () {
    console.log('Timeout complete.')
  }, 5000)
}

We are using the Promise variant of the handler, rather than callback-based. The docs seem to suggest this is different. So maybe this isn't relevant at all, but the bit about the timeout being "frozen" is pretty interesting :) might be worth looking into.

Start with the linked AWS Lambda Node.js handler documentation and compare its callback-based example with the Promise variant mentioned in the issue. Determine whether the description of context.callbackWaitsForEmptyEventLoop and the frozen timeout applies to both forms; done means the documentation discrepancy and required clarification are identified.