mtx.go

func GetValue(id int, wg *sync.WaitGroup, mtx *sync.RWMutex) (int, bool) {
	defer wg.Done()

	// Check the cache
	mtx.RLock()
	val, ok := cache[id]
	mtx.RUnlock()
	if ok {
		return val, ok
	}

	// Query the mock database
	time.Sleep(300 * time.Millisecond)
	mtx.Lock()
	val, ok = database[id]
	cache[id] = database[id]
	mtx.Unlock()
	return val, ok
}