I have to go.
Here are some basic suggestions:
Je dois partir.
Je dois y aller.
Il faut que je parte.
Il faut que j'y aille.
The last one is probably the most natural/casual. Many people pronounce it without the "il" and without the "e" in "que". So it sounds like "foke zhee I".
-
If you really meant you wanted to say "you have to go", then just change "je" to "tu" or "vous" (making sure to conjugate correctly, of course), for example "tu dois partir", "il faut que vous partiez", etc.
