go-lambda | purpose tool for creating and managing AWS Lambda instances | AWS library

I ended up determining that the type of "integration" you use matters. There's a couple including lambda, aws-proxy and lambda-proxy. By default it's lambda-proxy which means that all requests are handed to the function directly without any integration mapping or templates. You need lambda to do that.

The correct answer and what seems to be standard acceptable practice is to always send errors as nil and set the status code and response as the response message. If you send and error back Lambda will always return an internal error with 502.

This also means that logging and error tracking are completely up to you. In some cases this is the best approach, if you go the lambda integration route you'll have to define headers, accepted body and use the "integration mapping" process properly.

You have to make a decision which way you want to go with Lambda.

For full clarity, you're ALWAYS sending an events.APIGatewayProxyResponse back and nil as a second parameter from your handler. So a successful response would be: