import sync
import time

struct SafeCounter {
mut:
	mt sync.Mutex = sync.new_mutex()
pub mut:
	value map[string]int
}

fn (mut c SafeCounter) inc(key string) {
	c.mt.@lock()
	defer {
		c.mt.unlock()
	}
	c.value[key]++
}

fn (mut c SafeCounter) value(key string) int {
	c.mt.@lock()
	defer {
		c.mt.unlock()
	}
	return c.value[key]
}

fn main() {
	mut counter := &SafeCounter{}

	for i := 0; i < 5; i++ {
		spawn fn [mut counter] () {
			for j := 0; j < 100; j++ {
				counter.inc('key')
			}
		}()
	}

	time.sleep(1 * time.second)
	println(counter.value('key'))
}