refactor init and lambda.Start with the addition of middleware

main_middleware.go

var conf *ebs.Config

func init() {
        conf = ebs.NewConfig()
        secret := os.Getenv("EXTENSION_SECRET")
        helper = newService(decodeSecret(secret))
}

func main() {
        lambda.Start(
                ebs.MiddlewareCORS(conf,
                        handler,
                ),
        )
}