It was cancelled but there was no cliffhanger per se. I'd say that if it ran for much longer, it would have started to go downhill.
As such, cancellation probably saved it from overstaying its welcome and it did end at a high note.
I'd say that Sopranos, even though it was not cancelled, ended on a much larger cliffhanger than this series.
The point being, this is an amazing TV series that can be enjoyed from beginning till the end.
I am still astounded just how many people have seen sopranoes and shield, yet they know nothing about this series - even though it superior to either one of those.