I'm trying to use singletons for a specific class.

I did this trivially using the following in the "AppServicePrvider.php":

```
<?php

namespace App\Providers;

use App\Helpers\ApplicationFormHelper;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    public function boot()
    {

    }

    public function register()
    {
        $this->app->singleton(ApplicationFormHelper::class, function ($app) {
            return new ApplicationFormHelper();
        });
    }
}

```

I then included this class in my migration file like so:

```
<?php

use App\Helpers\ApplicationFormHelper;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateUsersTable extends Migration
{
    private $applicationFormHelper;

    public function __construct(ApplicationFormHelper $applicationFormHelper)
    {
        $this->applicationFormHelper = $applicationFormHelper;
    }

    public function up()
    {
        //...
    }

    public function down()
    {
        Schema::drop('users');
    }
}

```

However when I execute `php artisan migrate` I get the following error, indicating that dependency injection is not working. 

```
 [Symfony\Component\Debug\Exception\FatalThrowableError]                                                             
  Type error: Argument 1 passed to CreateUsersTable::__construct() must be an instance of App\Helpers\ApplicationFor  
  mHelper, none given, called in /home/vagrant/saroia/vendor/laravel/framework/src/Illuminate/Database/Migrations/Mi  
  grator.php on line 335   

```

Note that I have used this class is other places (e.g. in the routes file) with no problem. It seems to be only in the migrations file that this issue exists!