Share authentication via subdomains

So I see that Wix has support for subdomains, is there a way to share authentication from main domain to the sub domain? For example if they login into the main site, be able to share that login information for the sub domain so that they don’t have to login again?

I guess you can create a token to log the user in:

But maybe there’s a easier way (I’ve never tried to do that).
Let’s wait for some smarter answers.