private void EnsureUploadStarted()
        {
            lock (lockTask)
            {
                if (uploadTask == null)
                {
                    StorjApiClient client = new StorjApiClient(apiUrl);

                    if (Size > 0)
                    {
                        uploadTask = client.UploadStreamedAsync(Upload, fileName, Size);
                    }
                    else
                    {
                        uploadTask = client.UploadAsync(UploadAsync, fileName);
                    }
                }
            }
        }