Drupal 8: Process a queue programmatically

queue.php

$queue_factory = \Drupal::service('queue');
$queue_manager = \Drupal::service('plugin.manager.queue_worker');

$queue_worker = $queue_manager->createInstance('queue_name');

$queue = $queue_factory->get('queue_name');
$item = $queue->claimItem();
$queue_worker->processItem($item->data);