This is a tool to simlulate AWS lambda locally. It helps you develop go lambda function that you plan to put behind an Application Load Balancer.

Prerequisites

You'll need Docker installed. Your golang code binary will have to be compatible with Linux.

Usage

go get github.com/toff63/local-lambda

Then compile the code in go expecting requests coming from an ALB like:

 package main
    
 import (
     "context"
     "fmt"
    
     "github.com/aws/aws-lambda-go/events"
     "github.com/aws/aws-lambda-go/lambda"
 )
    
 func handleRequest(ctx context.Context, request events.ALBTargetGroupRequest) (events.ALBTargetGroupResponse, error) {
     fmt.Printf("Processing request data for traceId %s.\n", request.Headers["x-amzn-trace-id"])
     fmt.Printf("Body size = %d.\n", len(request.Body))
    
     fmt.Println("Headers:")
     for key, value := range request.Headers {
   fmt.Printf("    %s: %s\n", key, value)
     }
    
     return events.ALBTargetGroupResponse{Body: request.Body, StatusCode: 200, StatusDescription: "200 OK", IsBase64Encoded: false, Headers: map[string]string{}}, nil
 }
    
 func main() {
     lambda.Start(handleRequest)
 } 

Then run in a console

local-lambda --binary main

In another console you can send the http request like:

curl http://127.0.0.1:8080/hello

The local-lambda will show you logs that you would usually find in AWS Cloudwatch logs:

START RequestId: a9f293cc-8ce5-1790-bb74-dee907441c4b Version: $LATEST
Processing request data for traceId .
Body size = 0.
Headers:
    Accept: */*
    User-Agent: curl/7.58.0
END RequestId: a9f293cc-8ce5-1790-bb74-dee907441c4b
REPORT RequestId: a9f293cc-8ce5-1790-bb74-dee907441c4b  Duration: 1.25 ms       Billed Duration: 100 ms Memory Size: 1536 MB    Max Memory Used: 7 MB
{"statusCode":200,"statusDescription":"200 OK","headers":{},"multiValueHeaders":null,"body":"","isBase64Encoded":false}

Further work

This script is just a thin layer on top of lambci/docker-lambda so it is possible to extend this project to support further languages and type of events.