RealClock really calls time.Now().

Clock allows for injecting fake or real clocks into code that needs to do arbitrary things based on time.

PassiveClock allows for injecting fake or real clocks into code that needs to read the current time but does not support scheduling activity in the future.

Ticker defines the Ticker interface.

Timer allows for injecting fake or real timers into code that needs to do arbitrary things based on time.

WithDelayedExecution allows for injecting fake or real clocks into code that needs to make use of AfterFunc functionality.

WithTicker allows for injecting fake or real clocks into code that needs to do arbitrary things based on time.

WithTickerAndDelayedExecution allows for injecting fake or real clocks into code that needs Ticker and AfterFunc functionality.