module.config.php

//ou adicionar no array do module.config.php (ou outro config)

'service_manager' => array(
    'factories' => array(
        'Session' => function($sm) {
            return new Zend\Session\Container('ZF2napratica');
        },
        'Admin\Service\Auth' => function($sm) {
            $dbAdapter = $sm->get('DbAdapter');
            return new Admin\Service\Auth($dbAdapter);
        },
    )    
),