controller method
Implementation
ControllerTask controller(int tokenDownload) {
SelectDownload selectDow = checkDownload(tokenDownload);
if (!selectDow.exists || selectDow.status == null)
ControllerTask(exists: false);
TokenDownloadStatus status = selectDow.status!;
SelectTask st = _selectIsolate(status.isolateToken);
if (!st.exists) ControllerTask(exists: false);
TaskDownload dw = st.task!;
if (!dw.getStatus(tokenDownload)) ControllerTask(exists: false);
return ControllerTask(exists: true, controller: dw.statusDownload.stream);
}