Always promote on set

It's fine to conditionally promote on Get, to avoid blocking on a get
(see: #52) but a set _must_
promote else we can end with an entry in our buckets that isn't in our
list.

issue: #64

Author: karlseguin

cache.go

@@ -108,7 +108,10 @@ func (c *Cache) Get(key string) *Item {
 		return nil
 	}
 	if !item.Expired() {
-		c.promote(item)
+		select {
+		case c.promotables <- item:
+		default:
+		}
 	}
 	return item
 }
@@ -273,7 +276,7 @@ func (c *Cache) set(key string, value interface{}, duration time.Duration, track
 	if existing != nil {
 		c.deletables <- existing
 	}
-	c.promote(item)
+	c.promotables <- item
 	return item
 }
 
@@ -283,14 +286,6 @@ func (c *Cache) bucket(key string) *bucket {
 	return c.buckets[h.Sum32()&c.bucketMask]
 }
 
-func (c *Cache) promote(item *Item) {
-	select {
-	case c.promotables <- item:
-	default:
-	}
-
-}
-
 func (c *Cache) worker() {
 	defer close(c.control)
 	dropped := 0

layeredcache.go

@@ -68,7 +68,10 @@ func (c *LayeredCache) Get(primary, secondary string) *Item {
 		return nil
 	}
 	if item.expires > time.Now().UnixNano() {
-		c.promote(item)
+		select {
+		case c.promotables <- item:
+		default:
+		}
 	}
 	return item
 }