Aurora canvas boat cover

Is there a waterproof spray that I can spray on boat cover that will help with waterproofing it.

https://www.auroramarine.com/store/canvas-shield-waterproof-spray.html

recently put this on my cover, of course it quit raining once I treated it and I store my boat in the barn, but it was easy to apply and seems like it works based on the water bottle test I gave it.