"Hyvä" means "good". "Go" as in "go to places" would be "mennä" in Finnish ("Mene!" would be you ordering someone/thing to go.)
However, while in English you'd cheer someone/thing on (maybe you favourite sports team) with "Go team!" or something similar, in Finnish that is expressed with "hyvä" as in "Hyvä Suomi!", "Hyvä Anna!", "Hyvä, hyvä!".
So while "hyvä Suomi" directly translated would be "good Finland", its contextual meaning is "Go Finland!" etc.
Whoops, I stand corrected!!! Yay is simply an alternate spelling of yeah or yea, which have distinct pronunciations and meanings. (Yeah, an informal variant of yes, is pronounced “ya” and sometimes spelled that way; yea, which sounds like yay, survives as an affirmation in biblical contexts and as a counterpart to nay in voting contexts.