How to access InvocationContext CancellationTokenSource?

[rjdunnill-atwork]

I am using the current beta (released through NuGet), and I am curious as to what triggers the InvocationContext's CancellationTokenSource. I can't find any way to access the CancellationTokenSource outside of the command handler; can anyone advise how this CancellationTokenSource is meant to be used?

Among other things, I'd like to signal cancellation if CNTL-C is pressed. This is easy enough to do with a CancellationTokenSource of my own creation, but not with the one embedded in InvocationContext.