gomid

A middleware library written in Go

gomid is a middleware library which makes use of the decorator pattern to add functionality to basic functions. Usually, it is useful to add behaviour in our application without worrying about changing our current functionality. So, this middleware library easiness this kind of changes.

Check out our example with AWS Lambda functions to test its behaviour.

Usage example

Check out this file at main.go.

// https://github.com/d4n13l-4lf4/gomid/tree/main/examples/plain/main.go

package main

import (
	"context"
	"log"

	"github.com/d4n13l-4lf4/gomid/middleware"
)

func Adder(ctx context.Context, a int) (int, error) {
	log.Println(ctx)
	return a + 1, nil
}

func Multiplier(next middleware.Next) middleware.Next {
	return func(ctx context.Context, a any) (any, error) {
		newA := a.(int)

		return next(ctx, newA*2)
	}
}

func main() {
	fn := middleware.Wrap[func(context.Context, int) (any, error)](Adder).
		Add(Multiplier).
		Build()

	result, err := fn(context.Background(), 1)
	if err != nil {
		log.Panicln(err)
	}

	log.Printf("My result is %d", result)
}

AWS Lambda usage example

Check out a complete example at gomid-aws-example.

package main

import (
	"context"

	"github.com/aws/aws-lambda-go/events"
	"github.com/aws/aws-lambda-go/lambda"
	"github.com/d4n13l-4lf4/gomid-aws-example/auth"
	"github.com/d4n13l-4lf4/gomid-aws-example/hello"
	"github.com/d4n13l-4lf4/gomid/middleware"
)

func main() {
	greeter := hello.NewGreetingController(hello.Greet)
	chain := middleware.Wrap[func(context.Context, *events.APIGatewayProxyRequest) (any, error)](
		greeter.Greet,
	).
		Add(auth.AuthenticateUser(allowedUsers)).
		Build()

	lambda.Start(chain)
}