func (s *Stack) Push(elm string, done func()) {
    go func() {
        for !s.write.Load() {
        }

        s.data[atomic.AddInt32(s.end, 1)-1] = elm
        done()

        if atomic.LoadInt32(s.end) <= s.cap {
            s.write.Store(True)
        }
        s.read.Store(True)
    }()
}