Do cock rings keep you hard?

Hi all,I posted before about how I suddenly go soft just as I am about to top my boyfriend. It is the most mortifying experience ever and I have not tried since. So, quite a few of the replies said I should try using a cock ring. I just wanted to find out if anyone has had experience with them? Will they keep me hard, at least long enough to actually get my dick in my boyfriend, from there I will probably be good haha? Please can someone help.awks