"A task was canceled" issue when using dropbox chunked upload

 I'm writing a console application that uploads large files to dropbox. I want my program to resume failed upload whenever it accidentally exits or drops connection.  I retrive the uploadID and offset from a txt file to achieve this. 

But I constantly get "A task was canceled" issue. And I figured it is a timeout error. I have set "Timeout = TimeSpan.FromMinutes(30)" but it isn't working.

So how can I fix this?

Below is my code:

                try
                {
                    var httpClient = new HttpClient(new WebRequestHandler { ReadWriteTimeout = 10 * 1000 })
                    {
                        // Specify request level timeout which decides maximum time that can be spent on
                        // download/upload files.
                        Timeout = TimeSpan.FromMinutes(30)
                    };
                    var response = await _client.Core.Metadata.ChunkedUploadAsync(fragmentBuffer, count, uploadId, currentPosition, asTeamMember, cancellationToken).ConfigureAwait(false);
                    Console.Write("\r\n2try: {0} of {1} uploaded. uploadId: {2}\r\n", currentPosition, _dataSource.Length, uploadId);
                    uploadId = response.upload_id;
                    var testoffset = response.offset;
                    uploadoffset = testoffset;
                    var testexpires = response.expires;
                    currentPosition = endPosition;
                    Console.Write("\r\n3currentPosition: {0} endPosition: {1} testexpires: {2} count: {3} \r\n", currentPosition, endPosition, testexpires, count);
                }
                //catch (TaskCanceledException ex)
                //{
                //    // Check ex.CancellationToken.IsCancellationRequested here.
                //    // If false, it's pretty safe to assume it was a timeout.
                //    Console.WriteLine("\r\nerr TaskCanceledException: {0}\r\n", ex.CancellationToken.ToString());
                //}     

                catch (Exception e)
                {
                    //write down offset and uploadID to a txt
                    StreamWriter sw = new StreamWriter("1.txt");
                    sw.WriteLine(uploadoffset.ToString());
                    sw.WriteLine(uploadId.ToString());
                    sw.Close();
                    Console.WriteLine("7Err getting response:{0} .. Make sure you have connection again then press enter to resume. \n", e.Message);
                    Console.Write("7catch: currentPosition: {0} endPosition: {1}  \r\n", currentPosition, endPosition);
                    Console.ReadLine();
                }