$this->container = $this->getContainer();

$this->getApplication()

protected function execute(InputInterface $input, OutputInterface $output)
{
    $entityManager = $this->getContainer()->get('doctrine')->getEntityManager();

    // Code here
}

$this->container = $this->getApplication()->getKernel()->getContainer();

class UserCommand extends ContainerAwareCommand {
  private $em;

  public function __construct(?string $name = null, EntityManagerInterface $em) {
    parent::__construct($name);

    $this->em = $em;
  }

  protected function configure() {
    **name, desc, help code here**
  }

  protected function execute(InputInterface $input, OutputInterface $output) {
    $this->em->getRepository('App:Table')->findAll();
  }
}

class YourCmdCommand extends ContainerAwareCommand

$em = $this->getContainer()->get('doctrine.orm.entity_manager');

<?xml version="1.0" encoding="UTF-8" ?>

<container xmlns="http://symfony.com/schema/dic/services"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://symfony.com/schema/dic/services         http://symfony.com/schema/dic/services/services-1.0.xsd">

<services>
    <service id="EM_NAME.entity_manager" alias="doctrine.orm.entity_manager" />
</services>
</container>

$loader = new LoaderXmlFileLoader($container, new FileLocator(__DIR__.'/../Resources/config'));
$loader->load('model.xml');

$em = $this->getContainer()->get('EM_NAME.entity_manager');

$em->flush();

services:
    SOME_SERVICE:
        class: %parameter.class%
        arguments:
            - @EM_NAME.entity_manager