Williams-Goss, a junior guard, added six rebounds and seven assists as he torched the Dons for at least 30 points for the second time this season.
San Francisco shot well to lead for a good portion of the first half, until a late surge gave Gonzaga a 42-35 lead at halftime.
Williams-Goss scored 11 points as Gonzaga put together a 15-2 run that bracketed halftime to build a 52-37 lead early in the second.
Williams-Goss continued to score virtually at will, adding eight more points as Gonzaga built a 62-43 lead.
The Dons made only five of their first 20 shots in the second half.
Gonzaga, which has trailed only 6 percent of the time in games this season, fell behind 16-11 midway through the first half. The Zags clawed back and tied the game at 22-22 on Zach Collins' basket. Williams-Goss followed with a 3-pointer to put Gonzaga ahead for good.
San Francisco: The Dons gave Gonzaga one of its toughest league tests, losing 95-80 earlier this season. It was the most points scored this season against the Zags. The Dons are off to their best start since the 1999-2000 season.
Gonzaga: The Zags limit opponents to 37 percent shooting, second in the nation. Gonzaga has won at least 25 games in 13 of the past 14 seasons. Their 20 straight conference wins dating to last year are the longest streak in the nation.