Package time
Monotonic Clocks
Operating systems provide both a “wall clock,” which is subject to
changes for clock synchronization, and a “monotonic clock,” which is
not. The general rule is that the wall clock is for telling time and
the monotonic clock is for measuring time. Rather than split the API,
in this package the Time returned by time.Now contains both a wall
clock reading and a monotonic clock reading; later time-telling
operations use the wall clock reading, but later time-measuring
operations, specifically comparisons and subtractions, use the
monotonic clock reading.For example, this code always computes a positive elapsed time of
approximately 20 milliseconds, even if the wall clock is changed
during the operation being timed:start := time.Now() ... operation that takes 20 milliseconds ... t := time.Now() elapsed := t.Sub(start)Other idioms, such as time.Since(start), time.Until(deadline), and
time.Now().Before(deadline), are similarly robust against wall clock
resets.
Starting with Go 1.9 (released August 24, 2017), Go uses a monotonic clock for durations.
See Proposal: Monotonic Elapsed Time Measurements in Go.