When it comes to expressing necessity or obligation, there are various synonyms for the phrase "hast got to". One alternative would be "must", which is commonly used to convey that something is required or necessary. Another option could be "need to", which implies that completing a certain task or action is important or essential. "Have to" is also a commonly used synonym, as it suggests that there is no alternative or choice in the matter. Other synonyms include "ought to", "should", "got to", "needful", and "required". By using these synonyms, one can effectively convey the level of importance or obligation associated with a particular task or action.