Added cancelable

docs/faq.md

@@ -166,4 +166,6 @@ This is *almost* the same as the previous snippet except for the introduction of
 
 It is still worth keeping in mind that this is only a partial solution. Whenever `fis.read()` is blocked, cancelation will wait for that blocking to complete regardless of how long it takes. In other words, we still can't interrupt the `read()` function any more than we could with `interruptible`. All that `cancelable` is achieving here is allowing us to encode a more bespoke cancelation protocol for a particular effect, in this case in terms of `AtomicBoolean`.
 
+> Note: It is actually possible to implement a *proper* solution for cancelation here simply by applying the `cancelable` to the inner `blocking` effect and defining the handler to be `IO(fis.close())`, in addition to adding some error handling logic to catch the corresponding exception. This is a special case however, specific to `FileInputStream`, and doesn't make for as nice of an example. :-)
+
 The reason this is safe is it effectively leans entirely on *cooperative* cancelation. It's relatively common to have effects which cannot be canceled by normal means (and thus are, correctly, `uncancelable`) but which *can* be terminated early by using some ancillary protocol (in this case, an `AtomicBoolean`). Note that nothing is magic here and this is still fully safe with respect to backpressure and other finalizers. For example, `fis.close()` will still be run at the proper time, and cancelation of this fiber will only complete when all finalizers are done, exactly the same as non-`uncancelable` effects.