store.go

type Store struct {
    mutex sync.RWMutex
    data  map[string]int
}

func (s * Store) Read(key string) int, error {
    // ...
    defer s.mutex.RUnlock()
    s.mutex.RLock()
    // ...
    return val, nil
}

func (s * Store) Write(key string, value int) error {
    // ...
    defer s.mutex.Unlock()
    s.mutex.Lock()
    // ...
    return nil
}