Slim Framework 4 - Using $this when not in object (Medoo Framework) PHP

Question

I have updated my project based on Slim Framework to Slim 4 today. I'm working with the Medoo (database framework) here.

https://medoo.in/api/collaboration Here the Slim integration is explained:

use Medoo\Medoo;

$container = $app->getContainer();

$container['database'] = function () {
    return new Medoo([
        'database_type' => 'mysql',
        'database_name' => 'name',
        'server' => 'localhost',
        'username' => 'your_username',
        'password' => 'your_password'
    ]); 
};

The Query looks like:

$datas = $this->database->select("accounts", "*");

The error message I have received since the update is the following:

Got error 'PHP message: Slim Application Error:\nType: Error\nCode: 0\nMessage: Using $this when not in object

Have any of you had the problem? I have tried everything that I have in experience. I can't get any further here