I've often seen the word, "forego" in print, but don't remember seeing "forewent" as the past tense until reading Isabel Wilkerson's "The Warmth of Other Suns." Is it in common use and I've just not seen it, or is there a more common term?

I think most people use foregone.

And foregone is what a golfer says when he loses his ball.

But "foregone" is a past participle, not a simple past tense. Or have I forgotten basic grammar?

I have seen it, but rarely.

I've seen "forgone" a lot (a "foregone" conclusion). I think I've seen "forewent," but I can't cite when. It is much rarer.