How do I read the expiration date of server's SSL certificate via flurl?

Question

I would like to read a server's expiration date from the client side so that I can warn the user if the cert is about to expire within a certain amount of time. I'd like to do something similar to what's described here: SSL certificate pre-fetch .NET , but I'd like to do so with flurl since we've standardized on this as our http client mechanism. I wasn't able to find anything in the flurl documentation that would be helpful. Is it possible?