How change Config (base_url) on a Controller

I want build a website with subdomains, to a multi-language purpose, and that solution can help me.

Code eg.

Code:

public function initController(RequestInterface $request, ResponseInterface $response, LoggerInterface $logger)
    {
        //HERE something like that (but that dont work, of course)
        $config['base_url'] = 'https://en.test.com';

     
        // Do Not Edit This Line
        parent::initController($request, $response, $logger);

        // Preload any models, libraries, etc, here.

        // E.g.: $this->session = \Config\Services::session();
    }