APP_NAMESPACE do nothing..

Hi
My Controller in directories like theese
Application
  Controllers
    Blog
      Blog.php

I can not acces my controller 
<?php

namespace App\Controllers\Blog;
class Blog extends \CodeIgniter\Controller
{

}


My Solution:
Replacing namespace App\Controllers\Blog; with namespace Blog;

Hi
My Controller in directories like theese
Application
  Controllers
    Blog
      Blog.php

I can not acces my controller 
<?php

namespace App\Controllers\Blog;
class Blog extends \CodeIgniter\Controller
{

}


My Solution:
Replacing namespace App\Controllers\Blog; with namespace Blog;

namespace App\Controllers\Blog; should added into php file inside Blog folder and for Blog.php add namespace App\Controllers;

Keep calm.