I must be going now.

我现在得走了。

《牛津词典》

I must be going home; it's way past my bedtime.

我得回家了，早过了我的就寝时间了。

《牛津词典》

I must be going back at once.

我得马上回去。

《新英汉大辞典》

Here is an example, called "Hello,I Must be Going."

VOA: special.2009.07.19

I wish I had more time, but I must be going.
I wish I had more time, but I must be going.

I wish 课堂 - SpeakingMax英语口语达人

It's going to be cancelled next year. I won't get my money back.' Loans must be made even if the debt will be cancelled, for the simple reason that the problem of poverty is a terrible and persistent problem.

因为在来年贷款会被解除，他们就收不回自己的钱了,即使是债务会被免除，人们也必须给人借贷，这仅仅,是因为贫困是一个长久存在的可怕问题。

耶鲁公开课 - 旧约导论课程节选

And I was like, 'Oh, if I'm ever going to be as good as these guys, I must do something different.

WSJ: Menu

When Shane Warne was out to a freakish catch from Geraint Jones, I must admit I thought it was going to be tough to survive another eight or so overs.

BBC: DAY FIVE

Eddie O'Sullivan must be concerned because I do not think you are going to see anything new from Ireland.

BBC: Zinzan Brooke column