Cassie is one of the easiest characters for Goro to play neutral against honestly. Also, I didn't realize I was doing this before, but you can use Goro's walk speed to move around the map pretty quick if you know how to tap, walk back, tap the back button he can move around like the wave dashing REO mentioned. I think the ability for him to move around is overstated actually. I have a pretty easy time checking Cassie's back 1 with forward 3, down 4 etc due to the controlled movement.
He could use normalized movement, but like I tested in a video I made, his forward walk speed takes him about the same time to reach the opponent as say Kitana's forward walk speed and his forward dash is fine too.
His run is meh and while his movement isn't the greatest, the issue is highly exaggerated. This is like the cannot anti-air thing to me.