gotta=have got to必须；不得不
A: I'll catch you later, Connie. I gotta go!
B: So soon? Stay for another coffee.
A: Sorry, it's getting late. I'm outta here.
B: Come on, Rich, the night is still young.
A: No, I really must go. I've got to get up early tomorrow night. I'm off.
B: What about another serving of dessert?
A: That's tempting, but I've eaten so much that I think I am going to explode. And I must give a presentation at college tomorrow. I'll need to get my beauty sleep, or I might drop the ball.
B: In that case, I guess this really is goodbye. So long, Rich. It's been nice knowing you.