Sleep for the specified number of milliseconds.
Sleep
Sleep :: # (opaque)
Pause the current process for a requested duration.
Sleep for the specified number of seconds.
The duration is truncated to whole milliseconds, so Sleep.seconds!(1.5)
sleeps for 1500 ms. Negative and NaN durations return immediately, and
durations too long for the host to count saturate at about 584 years.