Add comment outlining TestContextCancel.
Stop calling `t.Errorf` from wrong goroutine.
Package up queueNoteFn expectation checking.
Add counting of goroutine in req1 exec fn.
Remove unnecessary assignment to `_`.
Make TestContextCancel wait on fake clock, to insulate timing check
from scheduler noise.
Factor goroutine counting out of queueset.go, into queueset_test.go,
where it matters.
Refactor promise: Use a simple channel-based implementation for normal
code, a mutex-based one for testing code.
Took all the panics out of queueset.go
Shrink the timeouts in promise tests to 1 second.
1db36ae3b3