There are plenty of synonyms for the phrase "have to go." Some of the most common alternatives include "need to leave," "must depart," "have an obligation to depart," and "need to bid farewell." Other options might include "time to head out," "must run along," "have to be on my way," or "need to hit the road." Depending on the context, some more informal or slangy alternatives might include phrases like "gotta bail," "time to bounce," or "need to peace out." No matter which alternative you choose, the important thing is to convey your intention to depart clearly and politely to those around you.