return err
	}

	wk, err := workers.New(workerSize)
	if err != nil {
		// invalid worker size.
		return err
	}

	retryAttempts := ri.RetryAttempts
	ctx, cancel := context.WithCancel(ctx)

	results := make(chan ObjectInfo, 100)
	if err := api.Walk(ctx, r.Bucket, r.Prefix, results, WalkOptions{
		Marker: lastObject,
		Filter: selectObj,
	}); err != nil {
		cancel()