"Hath to go" is an old-fashioned way of saying that someone has to leave or depart. There are several synonyms for this phrase, including "must depart," "need to go," "ought to leave," "have to take off," "must bid farewell," and "need to say goodbye." These phrases all convey the same sense of urgency or obligation to leave a particular place or situation. While "hath to go" may sound archaic, these other options are more modern and appropriate for everyday conversation. Whatever wording you choose, it's important to communicate clearly when you need to depart so that everyone involved is on the same page.