Doctrine service method to create a user that inserts a user so should use master connection

Service.php

<?php

class Service
{
    public function createUser(UserInterface $user)
    {
        $em = $this->getEntityManager();
        $conn = $em->getConnection();

        $conn->beginTransaction();

        try {
            $em->persist($user);
            $em->flush();

            $conn->commit();
        } catch (\Exception $e) {
            if ($conn->isTransactionActive()) {
                $conn->rollback();
            }

            $em->close();

            throw $e;
        }
    }
}