"At a go" refers to doing something in one attempt or without stopping. This phrase can be replaced by various synonyms depending on the context of the sentence. Some alternative phrases to use instead of "at a go" include "in one sitting," "in one shot," "all at once," "in one fell swoop," "in one breath," and "in one gulp." These synonyms can help vary the word choice in writing and add more emphasis to the action being described. It is important to choose the appropriate synonym to convey the intended meaning of the sentence effectively.