Function every 

pub fn every<F>(duration: Duration, fn_msg: F) -> Cmd
where
    F: FnOnce(SystemTime) -> Option<Box<dyn Msg>> + Send + Sync + 'static,

Every is a command that ticks in sync with the system clock. So, if you wanted to tick with the system clock every second, minute or hour you could use this. It’s also handy for having different things tick in sync.

Because we’re ticking with the system clock the tick will likely not run for the entire specified duration. For example, if we’re ticking for one minute and the clock is at 12:34:20 then the next tick will happen at 12:35:00, 40 seconds later.

To produce the command, pass a duration and a function which returns a message containing the time at which the tick occurred.

Beginners’ note: every sends a single message and won’t automatically dispatch messages at an interval. To do that, you’ll want to return another every command after receiving your tick message.