func (s *Service) Download(ctx context.Context, in *v1.DownloadReq) (*v1.DownloadResp, error) {
	f := excelize.NewFile()
	index, err := f.NewSheet("Sheet2")
	if err != nil {
		return nil, err
	}

	f.SetCellValue("Sheet2", "A2", "Hello world.")
	f.SetCellValue("Sheet1", "B2", 100)
	f.SetActiveSheet(index)

	if tr, ok := transport.FromServerContext(ctx); ok {
		if tr.Kind() == transport.KindHTTP {
			h := tr.(*http.Transport)
			disposition := fmt.Sprintf("attachment; filename=%s", "demo.xlsx")
			h.ReplyHeader().Set("Content-Type", "application/octet-stream")
			h.ReplyHeader().Set("Content-Disposition", disposition)
			h.ReplyHeader().Set("Access-Control-Expose-Headers", "Content-Disposition")

                         // get response obj
			if err := f.Write(h.Response()); err != nil {
				return nil, err
			}

			return nil, nil
		}
		if tr.Kind() == transport.KindGRPC {
			buffer, err := f.WriteToBuffer()
			if err != nil {
				s.log.ErrorContext(ctx, err.Error())
				return nil, err
			}
			return &v1.DownloadResp{Data: buffer.Bytes()}, nil
		}
	}

	return nil, errors.New("transport kind error")
}