这个怎么说呢？

我有一个问题。可能会有点啰嗦，但为了帮大家给我更准确的答案，首先我来解释一下自己的情况。

为了让我口语水平更上一层楼，我定期用某个语言学习网站来预订了汉语会话课。这是私人的在线课程，会议室里只有我和老师俩人。我之所以更喜欢这种课，是因为它提供了更多的说话机会。我附近没有会说汉语的人，所以虽然价格算是贵，但我觉得很值得订。

我还没有那么自在地用汉语聊天。要是我讲得太长，注意力会降低，开始很多结巴，所以我大部分的课是半个小时的。和让我感到愉快的老师聊聊，时间过得非常快，30分钟就像10分钟。有时候，30分钟后，尤其如果在我后面没有其他学生，有些老师还会继续聊天。一方面，我真的不介意，反而很高兴还有免费的说话机会。另一方面，我觉得自己只买了30分钟的课，却收到了超过30分钟的课，这样是不对的，心里有点内疚。

遇到这样的情况时，我会打岔，不好意思地向老师说：”老师，对不起我打断你一下，时间没有了”。我的意思简直是我们的30分钟都用光了。虽然我相信大家明白我的意思，但我也有预感这个说法不是标准的。我的问题是，如何用汉语自然地表达我的意思？

*其实我在网上查完后，已经找到了我想要的答案，但我也想练习一下写作能力，还想听听大家的答案，万一有别的答案。我找到的答案是“时间到了”。

How do you say this?

I have a question. This will perhaps make this text a bit too long, but to help everyone give me a more accurate answer, I'll first explain my situation.

To improve my speaking skills, I regularly book Chinese conversation lessons on a certain language learning website. These are private online lessons, only the teacher and I are in the virtual classroom. I prefer these lessons because they give me more opportunities to speak. Since there’s no one around me who speaks Chinese, the lessons are quite expensive, but I think they’re worth it.

I’m still not very comfortable chatting in Chinese. If I speak for too long, my focus drops, and I start to stutter a lot, so most of my lessons are 30 minutes long. When I talk with a teacher I enjoy talking with, time really flies, and 30 minutes feel like just 10. Sometimes, after 30 minutes—especially if there are no students after me—some teachers will continue chatting. On one hand, I don’t mind at all. If anything, I’m happy to get some extra speaking time for free. On the other hand, I feel guilty because I only paid for 30 minutes but ended up getting more. When this happens, I will interrupt by awkwardly telling the teacher, “老师，对不起我打断你一下，时间没有了。” What I mean is that our 30 minutes are up. I believe you all understand my meaning, but I have a feeling this isn’t the most natural way to say it. My question is: how do I naturally express this in Chinese?

*Actually, I already looked it up online and found the answer I was looking for, but I also wanted to practice my writing skills and hear other people’s answers—just in case there are different ways to say it. The answer I found is "时间到了".