How do I set up a password for my gmod server?

[Cash425]

Ok so im new to gmod. When I open my folder that says server.cfg it is blank. I put in sv_password "Inputpasswordhere" and when I save it and resart the server right after I saved it, the password security works and it asks for a password. If I then decide to log out and connect again it doesn't need a password and I can just log on without putting in a password. Even if I stop and restart the server it still doesn't need a password. Its like it needs the password once and then it unlocks it for everyone, forever. The only way I've got around this is opening the server.cfg and renaming my password and saving it and then restarting the server. I don't want to do this everytime I want to play gmod though. How can I make it so the password is permanent and everytime someone logs on no matter who it is, the server will ask for a password? Also I don't want to download any other crap like whitelist or gatekeeper. Thx