Unfortunately at this moment Canadian carriers will not offer the S10 5G model. 5G hasn't deployed yet and thus they won't be able to run tests on the device and make sure it will run smoothly. You will need to buy it online internationally which will cost you full price.
"It’s unlikely the 5G-enabled phone is coming to Canada anytime soon given the spectrum necessary for the phone to function is not available in Canada yet. The federal government has announced that spectrum auctions are set to take place in 2020 and 2021."