github.com/agext/clocks (go): Package clocks enables time travel (sort of)  The Clock interface groups all the time-passage-dependent features from the standard time package.  A "live" Clock is provided in this package giving pass-through access to the standard functionality.  A "manual" Clock is included as a separate package, because it is mostly useful for testing and it is rarely if ever needed in the actual program.
Keywords: testing|time|time-control