How do I instantly lock my computer when screen saver delay is on?
If you set your screen saver to require a password when exiting and then set one of the screen corners to turn the screen saver on, there you go instant turn my screen saver on gesture.

Unfortunately MacOS does not have a universal keystroke to lock the computer like Windows does.



If you have Mojave you can, the shortcut is there in the Apple menu:  ⌃ ⌘ Q