View all subscribed events?
In the above code example the event is KernelEvents::Request and checkAuthStatus is the method called when the Request event is dispatched.

You can use Drupal Console debug:event command to list all subscribers for a given event:

vendor/bin/drupal debug:event kernel.request

And that will give you something like:

  Drupal\Core\EventSubscriber\OptionsRequestSubscriber                   onRequest: 1000
  Drupal\Core\EventSubscriber\RedirectLeadingSlashesSubscriber           redirect: 1000
  Drupal\Core\EventSubscriber\AuthenticationSubscriber                   onKernelRequestAuthenticate: 300
  Drupal\language\EventSubscriber\LanguageRequestSubscriber              onKernelRequestLanguage: 255
  Drupal\Core\EventSubscriber\RedirectResponseSubscriber                 sanitizeDestination: 100
  Drupal\Core\EventSubscriber\AjaxResponseSubscriber                     onRequest: 50
  Symfony\Component\HttpKernel\EventListener\RouterListener              onKernelRequest: 32
  Drupal\Core\EventSubscriber\AuthenticationSubscriber                   onKernelRequestFilterProvider: 31
  Drupal\user\EventSubscriber\MaintenanceModeSubscriber                  onKernelRequestMaintenance: 31
  Drupal\Core\EventSubscriber\MaintenanceModeSubscriber                  onKernelRequestMaintenance: 30
  Drupal\Core\Routing\RoutePreloader                                     onRequest: 0
  Drupal\Core\EventSubscriber\ReplicaDatabaseIgnoreSubscriber            checkReplicaServer: 0


If you use Drush and have the devel module installed, you can do:

vendor/bin/drush devel-event kernel.request