In NewRateLimitingQueue how to get both old and new passed to UpdateFunc

How can i retrieve both old and new from the queue? https://github.com/kubernetes/client-go/blob/master/examples/workqueue/main.go#L181

		UpdateFunc: func(old interface{}, new interface{}) {
			key, err := cache.MetaNamespaceKeyFunc(new)
			if err == nil {
				queue.Add(key)
			}
		},

While processing each item c.processNextItem() how can I get both old and new?

  item, exists, err := c.informer.GetIndexer().GetByKey(event.key)

returns only the new.

Thanks a lot in advance.