Add testclient to check bug

client.go

@@ -402,13 +402,13 @@ func (c *Client) downloadChunked(ctx context.Context, req *http.Request, w *io.P
 	currentChunk := atomic.Uint32{}
 	for i := 0; i < maxRoutines; i++ {
 		go func() {
-			i := int(currentChunk.Add(1)) - 1
-			if i > len(chunks) {
+			chunkNumber := int(currentChunk.Add(1))
+			if chunkNumber > len(chunks) {
 				// no more chunks
 				return
 			}
 
-			chunk := &chunks[i]
+			chunk := &chunks[chunkNumber-1]
 			err := c.downloadChunk(req.Clone(cancelCtx), chunk)
 			close(chunk.data)
 

client_test.go

@@ -129,6 +129,15 @@ func TestGetVideoWithManifestURL(t *testing.T) {
 func TestGetStream(t *testing.T) {
 	assert, require := assert.New(t), require.New(t)
 
+	expectedSize := 988479
+
+	// Create testclient to enforce re-using of routines
+	testClient := Client{
+		Debug:       true,
+		MaxRoutines: 10,
+		ChunkSize:   int64(expectedSize) / 11,
+	}
+
 	// Download should not last longer than a minute.
 	// Otherwise we assume Youtube is throtteling us.
 	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
@@ -141,7 +150,7 @@ func TestGetStream(t *testing.T) {
 
 	reader, size, err := testClient.GetStreamContext(ctx, video, &video.Formats[0])
 	require.NoError(err)
-	assert.EqualValues(988479, size)
+	assert.EqualValues(expectedSize, size)
 
 	data, err := io.ReadAll(reader)
 	require.NoError(err)