time.nano -- effect providing nano time
time.nano is a timer that provides high precision but possibly low
accuracy. Such a timer is typically useful for timing the duration
of events, such as measuring the time it takes to perform some
time.nano may have a signficant drift compared to actual time, it might
not be the right source of time to, e.g., feed an alarm clock that should
wake you up at 6h30 every morning.