It is from your dashboard example

protected function login(
    {
        return Login::create()->
                ->headerText("Login")
                ->descriptionText("Sign in to your account")
                ->buttonText("Login")
                ->failedText("Wrong username or password")
                ->rightImageUrl("/assets/login/image.jpg");
                ->authenticate(function($uername,$password){
                    //You can make database connection in here to authenticate $username or password
                    //Return User class when it is authenticated

                    if($username==="johndoe" && $password==="johndoe") {
                        return User::create()
                                ->name("John Doe")
                                ->id(1)
                                ->roles(["guest"]);
                    }
                    return null;
                })
    }

Must be

protected function login()
    {
        return Login::create()
            ->headerText("Login")
            ->descriptionText("Sign in to your account")
            ->buttonText("Login")
            ->failedText("Wrong username or password")
            ->rightImageUrl("/assets/login/image.jpg")
        ->authenticate(function($username,$password){
        //You can make database connection in here to authenticate $username or password
        //Return User class when it is authenticated

        if($username==="johndoe" && $password==="johndoe") {
            return User::create()
                ->name("John Doe")
                ->id(1)
                ->roles(["guest"]);
        }
        return null;
    });
    }