CheckTimeout is the same as Check, but with a configurable timeout

CheckContext is the same as Check, but uses a context.Context for cancellation and timeout control

interestingGoroutines returns all goroutines we care about for the purpose of leak checking. It excludes testing or runtime ones.

Check snapshots the currently-running goroutines and returns a function to be run at the end of tests to see whether any goroutines leaked, waiting up

TestChangingStackTrace validates that a change in a preexisting goroutine's stack is not detected as a leaked goroutine.

TestSlowTest verifies that the timeout works on slow tests: it should be based on time after the test finishes rather than time after the test's start