timer.swift

import Foundation

let timer = DispatchSource.makeTimerSource(queue: .main)
timer.scheduleRepeating(wallDeadline: .now(), interval: .milliseconds(100), leeway: .milliseconds(100))
var count = 0
timer.setEventHandler(handler: {
    count += 1
    print("hello \(count)")
    if count >= 10 {
        exit(0)
    }
})
timer.resume()
dispatchMain()