stop Ticker after use to prevent the memory leak

https://github.com/golang/go/wiki/CodeReviewConcurrency#ticker-stop

backend/app/migrator/backup.go

@@ -27,6 +27,7 @@ type AutoBackup struct {
 func (ab AutoBackup) Do(ctx context.Context) {
 	log.Printf("[INFO] activate auto-backup for %s under %s, duration %s", ab.SiteID, ab.BackupLocation, ab.Duration)
 	tick := time.NewTicker(ab.Duration)
+	defer tick.Stop()
 	log.Printf("[DEBUG] first backup for %s at %s", ab.SiteID, time.Now().Add(ab.Duration))
 
 	for {

backend/app/store/image/image.go

@@ -215,6 +215,7 @@ func (s *Service) Close(ctx context.Context) {
 
 	waitForTerm := func(ctx context.Context) {
 		ticker := time.NewTicker(10 * time.Millisecond)
+		defer ticker.Stop()
 		for {
 			select {
 			case <-ctx.Done():