Straight from my Model 3’s user manual:
Green Traffic Light Chime: In Canada and U.S.: If on, a chime will sound when you are waiting at a red traffic light and the light turns green. If you are not actively using Traffic-Aware Cruise Control and are waiting at a red light with a car in front...
The Go Chime is not an indicator that it is safe to go. It’s meant to get your attention that traffic is moving ahead of you after being stopped behind another car for a bit. You are still responsible for checking traffic conditions before moving.