getFile method
Use this method to get basic info about a file and prepare it for downloading.
For the moment, bots can download files of up to 20MB in size.
On success, a File object is returned.
The file can then be downloaded using download method.
It is guaranteed that the link will be valid for at least 1 hour.
When the link expires, a new one can be requested by calling getFile again.
Implementation
Future<File> getFile(String fileId) {
return _client.apiCall(_token, 'getFile', {'file_id': fileId});
}