lambda-go-extras

lambda-go-extras

This module provides a middleware layer for github.com/aws/aws-lambda-go. This project is heavily based on https://github.com/justinas/alice.

Why?

Having used the github.com/aws/aws-lambda-go package for a while now I have found it annoying switching between the Go standard libraries http package and this library. After some review I think the thing I miss the most is the ability to chain a list of handlers, with each link responsible for a part of the puzzle.

Being able to compose these chains offers a lot of flexibility and reuse across projects.

Given the default way of using the github.com/aws/aws-lambda-go is via the Start(handler interface{}) function, which is very flexible, but not easily extended due it's dynamic nature. So I have moved to using the less used func StartHandler(handler Handler) which is more idiomatic with its Handler being just an interface with a single Invoke method. This module has extended this with a simple middleware chain inspired by alice as mentioned above.

Usage

This illustrates how easy it is to dump the input and output payloads using a simple middleware chain.

package main

import (
	"context"
	"fmt"

	"github.com/aws/aws-lambda-go/lambda"
	"github.com/wolfeidau/lambda-go-extras/lambdaextras"
	lmw "github.com/wolfeidau/lambda-go-extras/middleware"
)

func main() {

	ch := lmw.New(logEvent).ThenFunc(processEvent)

	lambda.StartHandler(ch)
}

func logEvent(next lambda.Handler) lambda.Handler {
	return lambdaextras.HandlerFunc(func(ctx context.Context, payload []byte) ([]byte, error) {

		fmt.Println(string(payload))

		result, err := next.Invoke(ctx, payload)

		fmt.Println(string(result))

		return result, err
	})
}

func processEvent(ctx context.Context, payload []byte) ([]byte, error) {
	return []byte("ok"), nil
}

License

This code was authored by Mark Wolfe and is licensed under the Apache 2.0 license.