pkg/services/alerting/reader.go: Fix should use for range instead of for { select {} }.

$ gometalinter --vendor --deadline 10m --disable-all --enable=megacheck ./...
pkg/services/alerting/reader.go:37:2:warning: should use for range instead of for { select {} } (S1000) (megacheck)

pkg/services/alerting/reader.go

@@ -34,11 +34,8 @@ func NewRuleReader() *DefaultRuleReader {
 func (arr *DefaultRuleReader) initReader() {
 	heartbeat := time.NewTicker(time.Second * 10)
 
-	for {
-		select {
-		case <-heartbeat.C:
-			arr.heartbeat()
-		}
+	for range heartbeat.C {
+		arr.heartbeat()
 	}
 }