Implementation of watchdog using GCD

gcd watchdog

CGFloat timeout = 2;

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
_timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);

dispatch_source_set_timer(_timer, dispatch_time(DISPATCH_TIME_NOW, timeout * NSEC_PER_SEC), DISPATCH_TIME_FOREVER, 0);
dispatch_source_set_event_handler(_timer, ^{
    // custom code
    
    dispatch_source_cancel(_timer);
});
dispatch_resume(_timer);

//
dispatch_source_cancel(_timer);

dispatch_release(_timer);