module CountDownLatch:sig..end
type t
val make : int32 -> tmake n returns a countdown latch waiting for n threads.
Raises Invalid_argument if n is negative.
val await : t -> unit
Raises Runtime.Interrupted if the thread is interrupted.
val await_time : t -> int64 -> TimeUnit.t -> boolawait_time c t u is similar to await c, except that the current
thread will at most wait for t (time value whose unit is u).
Raises Runtime.Interrupted if the thread is interrupted.
val count_down : t -> unitval get_count : t -> int64