Demonstrates how to generate different types of errors for AWS Lambda Step Functions, so that Retry/Catch can distinguish between different kinds of errors.

err_handler.go

package main

import (
	"context"
	"fmt"
	"github.com/aws/aws-lambda-go/lambda"
	"log"
)


func FailHander(ctx context.Context, req ErrorRequest) error {
	if req.Outcome == "base" {
		return fmt.Errorf("bog-standard error")
	} else if req.Outcome == "fancy" {
		return &HandlerError{"error from a failed handler"}
	} else {
		log.Println("This was good, really good :)")
		return nil
	}
}

type HandlerError struct {
	Detail string `json:"detail"`
}

func (e *HandlerError) Error() string {
	return e.Detail
}

type ErrorRequest struct {
	Outcome string `json:"outcome"`
}

func main() {
	lambda.Start(FailHander)
}

ErrorStateMachine.json

{
  "Comment": "A state machine to experiment with errors",
  "StartAt": "Error Handler",
  "States": {
    "Error Handler": {
      "Type": "Task",
      "Resource": "arn:aws:states:::lambda:invoke",
      "OutputPath": "$.Payload",
      "Parameters": {
        "Payload.$": "$",
        "FunctionName": "arn:aws:<AWS REGION>:<YOUR AWS ACCOUNT ID HERE>:function:book-error:$LATEST"
      },
      "Catch": [
        {
          "ErrorEquals": [
            "errorString"
          ],
          "Next": "Error String"
        },
        {
          "ErrorEquals": [
            "HandlerError"
          ],
          "Next": "Handler Error"
        }
      ],
      "End": true
    },
    "Handler Error": {
      "Type": "Fail"
    },
    "Error String": {
      "Type": "Succeed"
    }
  }
}