Exemplo de uso do PHP-DI e Slim

di-config.php

<?php

use App\Infra\DbConnection;
use Psr\Container\ContainerInterface;

return [
  'db.name' => getenv("DB_NAME"),
  'db.user' => getenv("DB_USER"),
  'db.password' => getenv("DB_PASSWORD"),
  DbConnection::class => function (ContainerInterface $c) {
    return new DbConnection($c->get('db.name'), $c->get('db.user'), $c->get('db.password'));
  },
];

index.php

<?php
require_once "vendor/autoload.php";

use DI\ContainerBuilder;
use Slim\Factory\AppFactory;
use App\Controller\LoginController;

$containerBuilder = new ContainerBuilder();
$containerBuilder->addDefinitions('di-config.php');

AppFactory::setContainer($container);
$app = AppFactory::create();

$app->post('/login', "{LoginController::class}:login");

$app->addRoutingMiddleware();
$app->addErrorMiddleware(true, true, true);

LoginController.php

<?php

namespace App\Controller;

use App\Repository\UsuarioRepository;
use Psr\Container\ContainerInterface;
use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;

class LoginController extends Controller
{

    private UsuarioRepository $repository;

    public function __construct(ContainerInterface $container)
    {
        parent::__construct($container);
        $this->repository = $this->container->get(UsuarioRepository::class);
    }

    public function login(Request $request, Response $response, array $args): Response
    {

        $login = $this->getParam($request, 'login', '');
        $password = $this->getParam($request, 'password', '');

        try {
            $user = $this->repository->auth($login, $password);
        } catch (\DomainException $e) {

            $new_response = $response->withStatus(403);
            return $new_response;
        }

        return $this->toJson($response, ['jwt' => $usuario->getId(), 'user' => $user]);
    }
}