Provides two implementations of Recorder-- one that is non-blocking
like the original version and one that provides a blocking channel
to avoid busy waiting or racing in tests when no other synchronization
is available.
It is possible to trigger the time.After case if the timer went off
between time.After setting the timer for its channel and the time that
select looked at the channel. So it needs to be longer.
refer: https://groups.google.com/forum/#!topic/golang-nuts/1tjcV80ccq8
