Along the same lines, if you want to make your own AWS Lambda /API Gateway version of this:

    def lambda_handler(event, context):
        return {
            'statusCode': '200',
            'headers': None,
            'body': event.get('requestContext', {}).get('identity', {}).get('sourceIp', 'unknown')
        }

I do this, though my lambda is a bit more complex in practice, since I have some triggers that say "if this thing reports a new IP, do something".

Of course, AWS provides this basic service as checkip.amazonaws.com