suggestion: support Ctrl+C handling

When the application is terminated by the user (e.g. presses Ctrl+C), it terminates immediately.

The application may want to do something, for example: kill some child processes it has started.

It is possible to handle this using Console.CancelKeyPress. It would be nicer if this was an API pattern in CommandLineUtils. For example: a CancellationToken gets passed to OnExecuteAsync. This token is canceled when the user terminates the application.

[tmds]

I’ve added this to System.CommandLine in https://github.com/dotnet/command-line-api/pull/290. This is the documentation for that: https://github.com/dotnet/command-line-api/wiki/Process-termination-handling.

[natemcmaster]

Interesting idea. I’m thinking through some implementation ideas and it might be quirky when we get into async land. IIRC, callbacks on CancellationTokenSource.Cancel() should run inline, but wouldn’t it still be possible for the CancelKeyPress event handler terminate before some async continuations finish?

The way we solved this in aspnet and dotnet-watch is that the first CTRL+C invocation begins graceful shutdown and sets ConsoleCancelEventArgs.Cancel to true. The second time CTRL+C is raised we force exit the process. I’m wondering if that would be a good pattern to use by default, or if that should be something users configure.