How to create shortcode for auto login after registration

I've a code for auto-login after registration which is:

function auto_login_new_user( $user_id ) {
    wp_set_current_user($user_id);
    wp_set_auth_cookie($user_id);
    $request = $_SERVER["HTTP_REFERER"];
    wp_redirect($request);
    exit;
}
add_action( 'user_register', 'auto_login_new_user' );

what I need is to create a shortcode to control the time of redirect, I don't want it to redirect after $userID = wp_insert_user( $userDataArr );

I want the redirect to happen after adding some code for extra fields like so update_user_meta( $userID, $fieldsArr[$fieldN], $value);

I was thinking that I can do so by butting the ADD_ACTION code inside shortcode funtion

function my_login_shortcode(){
    add_action( 'user_register', 'auto_login_new_user' );
}
add_shortcode('mogincode','my_login_shortcode');

how can I do that ?