Support for custom error types

[advdv]

This might be a long shot but on the 16th of march a feature was added to AWS Step Functions that allows you to drive state transitions based on specific errors from your Lambda functions; a feature I was waiting for. A NodeJS example of this can be found here: https://docs.aws.amazon.com/step-functions/latest/dg/tutorial-handling-error-conditions.html and the announcement here https://aws.amazon.com/about-aws/whats-new/2017/03/aws-step-functions-adds-customized-error-handling-for-aws-lambda-functions/

They didn't add matching based on JSON fields or string matching and only check the error type as returned by the runtime. With the awesome wrapper Go you guys made it currently doesn't seem possible (https://github.com/eawsy/aws-lambda-go-shim/blob/81ecb522e11dbd6096b6219fa66d9992e3410b1f/src/proxy.py#L48) to use this feature, is this correct? Is there any way of adding this?

You guys rock! Cheers, Ad

[fsenart]

@advanderveer ok ok. I think I got it. I've made a simple poc and see how to do the job. Let me one day or two ;)

PS: Thx very much for your issue, I think this new feature can bring the shim to a new level.

[fsenart]

@advanderveer sorry for the delay, I was very busy. Update your docker image and that's is, you can return custom errors and use it in step functions:

package main

import (
	"encoding/json"

	"github.com/eawsy/aws-lambda-go-core/service/lambda/runtime"
)

type CustomError struct {
	s string
}

func (e *CustomError) Error() string {
	return e.s
}

func Handle(json.RawMessage, *runtime.Context) (interface{}, error) {
	return nil, &CustomError{"something bad happened"}
}

[advdv]

Awesome! Thank you