Pass CancellationToken to AsyncCommand.ExecuteAsync()?

[wjrogers]

I gave Spectre.Console.Cli a spin by porting an existing project, and one of the pain points was co-operative cancellation of asynchronous commands. The library I had been using previously passed a CancellationToken to its abstract "execute" method, so I had a bunch of existing code that expected to receive one. I had to resort to constructor injection of IHostApplicationLifetime to get its StoppingToken in every command, which is a lot of boilerplate when you have more than a trivial number of commands.

It seems like Spectre could add a CommandContext.CancellationToken property without breaking its existing API. By default, this could be CancellationToken.None. Then, an overload could be added to CommandApp.RunAsync() that accepts a CancellationToken and propagates it to the CommandContext. (Its CanBeCanceled property would allow implementers to discover whether cancellation is "wired up" or not.)

Would you be interested in this feature? I think I could manage a pull request that adds it.

[nils-a]

#701 is probably related to this