Update cache.rst

Wrap example in function with autowire `TagAwareCacheInterface` pool.

Author: pavelmaca

cache.rst

@@ -486,22 +486,27 @@ to be able to invalidate the cache more efficient. One way to achieve that is to
 use cache tags. One or more tags could be added to the cache item. All items with
 the same key could be invalidate with one function call::
 
+    use Symfony\Contracts\Cache\ItemInterface;
     use Symfony\Contracts\Cache\TagAwareCacheInterface;
 
-    $value0 = $pool->get('item_0', function (TagAwareCacheInterface $item) {
-        $item->tag(['foo', 'bar'])
+    // using autowiring
+    public function listProducts(TagAwareCacheInterface $pool)
+    {
+        $value0 = $pool->get('item_0', function (ItemInterface $item) {
+            $item->tag(['foo', 'bar']);
 
-        return 'debug';
-    });
+            return 'debug';
+        });
 
-    $value1 = $pool->get('item_1', function (TagAwareCacheInterface $item) {
-        $item->tag('foo')
+        $value1 = $pool->get('item_1', function (ItemInterface $item) {
+            $item->tag('foo');
 
-        return 'debug';
-    });
+            return 'debug';
+        });
 
-    // Remove all cache keys tagged with "bar"
-    $pool->invalidateTags(['bar']);
+        // Remove all cache keys tagged with "bar"
+        $pool->invalidateTags(['bar']);
+    }
 
 The cache adapter needs to implement :class:`Symfony\\Contracts\\Cache\\TagAwareCacheInterface``
 to enable this feature. This could be added by using the following configuration.