private void Update()
    {
        if (state == BGMSTATE.START)
        {
            time += Time.deltaTime;
            audioSource.volume = settingM.BGM * settingM.MasterVolume * time * 0.5f;

            if (time >= 1)
            {
                state = BGMSTATE.PLAY;
            }
        }
        else if (state == BGMSTATE.PLAY)
        {
            audioSource.volume = settingM.BGM * settingM.MasterVolume * 0.5f;
            time = 1;
        }
        else if (state == BGMSTATE.FINISH)
        {
            if (time <= 0)
            {
                time = 0;
            }

            time -= Time.deltaTime;
            audioSource.volume = settingM.BGM * settingM.MasterVolume * time * 0.5f;
        }
    }
 private void Start()
 {
     state = BGMSTATE.START;
 }
 public void SetState(BGMSTATE state)
 {
     this.state = state;
 }