asynchronous任务上的TaskCanceledException C＃

我有一个C＃ConsoleApplication与下面的代码（片段）：

Task exportTask = Task.Run(async () => { try { // code IList<OmbisLeistungsPosition> leistungsPositionen = getItems(); string result = await ombis.Write(leistungsPositionen); // code } catch (Exception e) { Email.SendErrorToDeveloper(e.ToString()); Console.WriteLine(e.Message); } }); exportTask.Wait(); internal async Task<string> Write(IList<OmbisLeistungsPosition> leistungsPositionen) { HttpClient httpRequest = GetDigestHttpRequest(); string json = JsonConvert.SerializeObject(leistungsPositionen); StringContent content = new StringContent(json, Encoding.UTF8, "application/json"); HttpResponseMessage response = await httpRequest.PostAsync(UrlOmbisLeistungspositionen, content); string result = await response.Content.ReadAsStringAsync(); return result; } 

它PostAsync的预期结果是可以的，但是我在PostAsync被调用的行上得到以下exception：

 System.Threading.Tasks.TaskCanceledException: A task was canceled. at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() at HGV.Personalberatung.Fakturierung770.Ombis.<Write>d__8.MoveNext() in C:\Users\EBorsoi\Documents\Git\HGV.Personalberatung.Fakturierung770.ServerApi\HGV.Personalberatung.Fakturierung770\Ombis.cs:line 229 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() at HGV.Personalberatung.Fakturierung770.Program.<>c__DisplayClass3_0.<<ExportToOmbis>b__0>d.MoveNext() in C:\Users\EBorsoi\Documents\Git\HGV.Personalberatung.Fakturierung770.ServerApi\HGV.Personalberatung.Fakturierung770\Program.cs:line 109 

为什么系统抛出exception？ 这是什么意思？ 我如何解决它？