Add CancellationToken support on async calls

[brianfeucht]

It is considered a best practice to provide a CancellationToken to allow for the cancellation of tasks.

It doesn't appear that any of the async code in this library has any support for passing in a CancellationToken. This means if a query end up being long running there is no way for the caller to abort a request. This can cause problems for things like Windows Services where the expectation is to respond quickly to shutdown requests.

[yj7o5]

Hi @droyad, I have been lately using this client at work and have noticed the absence of CancellationToken can I take a stab at the following issue?

[matt-richardson]

Hi @yj7o5 - sure, go for it! PRs definitely appreciated 👍

[yj7o5]

Thanks guys, feel free to assign it to me and I'll get the PR in a day or two. :)

[yj7o5]

@matt-richardson PR submitted for your review! Thanks.