what is it" chorus was like "so long, so long"

can you guys help me?

was at a dance club and heard what sounded to be an old classic (70's? 80's) by a group that had a chorus "so long, so long" (last two words sung at same pitch) - very danceable - very fun - can't find it no matter how many Googles I do, but it should be out there somewhere.... an established hit

any help would be sooooo appreciated

I'm hoping someone can help me find out who sings the song we're going through i think is the name of the song
thanks wendy

the only song of the 70's/80's called "so long" is the one of the Abba.....