A more honest approach would be to require a signup before an action takes place. Letting a user do some things, get invested, and then drop a signup requirement on them is a dark pattern
Only then was I asked to log in with a Google account. But I don't even have a Google account... So, I just configured the whole session for absolutely no useful reason. Not that it wasted a lot of my time but it is generally a more annoying thing to happen. Handle the login first, or announce that it is required with some disclaimer before the user performs any action.