Function timeout_add_full 

pub fn timeout_add_full<F>(
    interval: Duration,
    priority: Priority,
    func: F,
) -> SourceId
where
    F: FnMut() -> ControlFlow + Send + 'static,

Adds a closure to be called by the default main loop at regular intervals with millisecond granularity.

func will be called repeatedly every interval milliseconds with priority until it returns ControlFlow::Break. Precise timing is not guaranteed, the timeout may be delayed by other events. Prefer timeout_add_seconds when millisecond precision is not necessary.

The default main loop almost always is the main loop of the main thread. Thus, the closure is called on the main thread.