Zend framework 2 Rest API : Calls getList() instead of get($id) function

Following is my module config file

return array(
'controllers' => array(
    'invokables' => array(
        'RSMobile\Controller\User' => 'RSMobile\Controller\UserController',
    ),
),

// Routes for API calls
'router' => array(
    'routes' => array(

        'rsmobile' => array(
            'type' => 'segment',
            'options' => array(
                'route' => '/rsmobile',
                'defaults' => array(
                    'controller' => 'RSMobile\Controller\User',
                )
            ),

            // Child routes
            'child_routes' => array(
                // Route for "user" API
                'user' => array(
                    'type' => 'segment',
                    'options' => array(
                        'route' => '/user[/:id]',
                        'constraints' => array(
                                               'id'     => '[0-9a-zA-Z]+',
                                                              ),
                        'defaults' => array(
                            'controller' => 'RSMobile\Controller\User',
                        )
                    ),
                ),
          )

Question:

I have extends AbstractRestfulController in UserController file but, when i call this with www.example.com/rsmobile/user?userid=1 it call get-list instead of get.

Any Light on path would be helpful

Thanks