implement a goroutine pool

turns out b2 doesn't like it if you use too many threads

main.go

@@ -24,7 +24,7 @@ var secretAccessKey = flag.String("secret-access-key", "", "aws secret key")
 var updateExpiresWithin = flag.Int("update-expires-within", 0, "only update objects whose lock expires within this many seconds (default 0)")
 var lockFor = flag.Int("lock-for", 90*24*3600, "how many seconds to renew the object lock for (default 90 days)")
 
-var wg sync.WaitGroup
+var threadCount = flag.Int("threads", 1024, "how many objects to operate on at a time")
 
 func main() {
 	flag.Parse()
@@ -52,6 +52,17 @@ func main() {
 		Bucket: bucket,
 	})
 
+	objectQueue := make(chan string)
+
+	var wg sync.WaitGroup
+	for i := 0; i < *threadCount; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			queueWorker(svc, objectQueue)
+		}()
+	}
+
 	for paginator.HasMorePages() {
 		page, err := paginator.NextPage(context.TODO())
 		if err != nil {
@@ -59,17 +70,24 @@ func main() {
 		}
 
 		for _, item := range page.Contents {
-			wg.Add(1)
-			go func(svc *s3.Client, key string) {
-				defer wg.Done()
-				checkAndRenewObjectLock(svc, key)
-			}(svc, *item.Key)
+			objectQueue <- *item.Key
 		}
 	}
 
+	close(objectQueue)
 	wg.Wait()
 }
 
+func queueWorker(svc *s3.Client, inQueue chan string) {
+	for {
+		object, more := <-inQueue
+		if !more {
+			return
+		}
+		checkAndRenewObjectLock(svc, object)
+	}
+}
+
 func checkAndRenewObjectLock(svc *s3.Client, object string) {
 	updateHold := false
 	if *updateExpiresWithin == 0 {