Investigate dotnet-watch failures

[jkotalik]

https://dev.azure.com/dnceng/public/_build/results?buildId=706059&view=ms.vss-test-web.build-test-results-tab&runId=21867388&resultId=121648&paneView=debug

System.TimeoutException : The operation at /_/src/Tools/dotnet-watch/test/ProgramTests.cs:43 timed out after reaching the limit of 30000ms.

   at Microsoft.AspNetCore.Testing.TaskExtensions.TimeoutAfter[T](Task`1 task, TimeSpan timeout, String filePath, Int32 lineNumber) in /_/src/Testing/src/TaskExtensions.cs:line 33
   at Microsoft.DotNet.Watcher.Tools.Tests.ProgramTests.ConsoleCancelKey() in /_/src/Tools/dotnet-watch/test/ProgramTests.cs:line 43
--- End of stack trace from previous location ---

[BrennanConroy]

There is a core dump file for this failure. I'm assuming it is for the process launched by dotnet-watch.

The dump file doesn't show any obvious reason for a crash, all threads show stop reason as "SIGSTOP" which is generally graceful.

[pranavkm]

We haven't noticed these failures since migrating dotnet-watch to the SDK.

[MiYanni]

Howdy. This issue was listed as the reason for this test, ConsoleCancelKey, being skipped. However, when I unskip it, the test runs RunAsync completely prior to hitting ConsoleCancelKey, seen here. The result is that _cancelKeyPress has already been subscribed to and then unsubscribed to by the time it is reached here, thus causing a NRE since without any subscribers, it is null. I believe the intent is that ConsoleCancelKey should be called while the RunAsync operation is happening. Is there a dotnet watch command that can cause that to happen so that this test works properly?