Cannot inject Templating on Symfony 4 Service

You have to install symfony/templating

composer require symfony/templating

change a little bit config/packages/framework.yaml

framework:
    templating:
        engines:
            - twig

I managed to do it with Twig Environment and HTTP Response

<?php

namespace App\Controller;

use Twig\Environment;
use Symfony\Component\HttpFoundation\Response;

class MyClass
{
    private $twig;

    public function __construct(Environment $twig)
    {
        $this->twig = $twig;
    }

    public function renderTemplateAction($msg)
    {
        return new Response($this->twig->render('myTemplate.html.twig'));
    }
}

Most likely you don't have Templating included in your project, in Symfony 4 you have to require it explicitly:

composer require symfony/templating