use of channels

eth/stagedsync/stage_headers.go

@@ -202,22 +202,21 @@ func HeadersDownward(
 
 	stopped := false
 	prevProgress := header.Number.Uint64()
+	doneCh := make(chan bool)
 	go func() {
 		for {
-			timer := time.NewTimer(1 * time.Second)
 			select {
 			case <-ctx.Done():
-				stopped = true
+				doneCh <- true
+				return
 			case <-logEvery.C:
 				diff := prevProgress - cfg.hd.Progress()
 				if cfg.hd.Progress() <= prevProgress {
 					log.Info("Wrote Block Headers backwards", "from", header.Number.Uint64(),
 						"now", cfg.hd.Progress(), "blk/sec", float64(diff)/float64(logInterval/time.Second))
 					prevProgress = cfg.hd.Progress()
 				}
-			}
-			timer.Stop()
-			if stopped {
+			case <-doneCh:
 				return
 			}
 		}
@@ -239,7 +238,8 @@ func HeadersDownward(
 			req = cfg.hd.RequestMoreHeadersForPOS()
 			_, sentToPeer = cfg.headerReqSend(ctx, &req)
 			if !sentToPeer {
-				time.Sleep(30 * time.Millisecond)
+				timer := time.NewTimer(30 * time.Millisecond)
+				timer.Stop()
 			}
 		}
 		// Load headers into the database
@@ -250,11 +250,17 @@ func HeadersDownward(
 		if cfg.hd.Synced() { // We do not break unless there best header changed
 			stopped = true
 		}
+		select {
+		case <-doneCh:
+			stopped = true
+		default:
+		}
 	}
 	// If the user stopped it, we dont update anything
 	if !cfg.hd.Synced() {
 		return nil
 	}
+	doneCh <- true
 	if err := headerCollector.Load(tx, kv.Headers, etl.IdentityLoadFunc, etl.TransformArgs{
 		LogDetailsLoad: func(k, v []byte) (additionalLogArguments []interface{}) {
 			return []interface{}{"block", binary.BigEndian.Uint64(k)}