bugfix

cache/cachemap.go

@@ -234,5 +234,7 @@ func (s *cacheMap) Clear() {
 // for garbage collector
 func destroyCacheMap(m *CacheMap) {
 	close(m.stopCleanerChan)
-	close(m.cleanedEventChan)
+	if m.cleanedEventChan != nil {
+		close(m.cleanedEventChan)
+	}
 }