"Go fetch" is a common phrase used to instruct someone to go and retrieve something for you. However, there are several synonyms one can use to express the same idea. One option is to say "go and get" or "go and bring". Another similar phrase is "go retrieve". One can also say "go after" or "go find". For a more casual tone, one can simply say "go grab". Other synonyms to consider are "fetch it" or "bring it back". Regardless of the word choice, the phrase used ultimately serves the same purpose - to instruct someone to go and retrieve something.