Lots of people fret that they havent learned to canter sooner. But I have met others who were put off riding by being allowed or made to canter too soon.
Please take care. Cantering on a horse that will not stop may not be safe for a beginner, especially in a school arena with corners. On the other hand if you are out hacking and cantering beside another horse, that may be a good way to learn.
By the way, many polo ponies are ridden and trained to canter and not trot. But they are trained to have brakes.