aller (to go) should be a 1st group verb but it is an irregular verb; therefore it is a 3rd group verb:

aller	to go
je vais	I go
tu vas	you go
il va	he goes
nous allons	we go
vous allez	you go
ils vont	they go

NB: "vas" and "va" should be pronounced the same way. Do not pronounce the final "s".