Control + ⌘ + Q locks the Mac. Your apps keep running and Touch ID or your password unlocks it.
Lock your screen instantly
⌃ Control+⌘ Cmd+Q
Your computer or browser handles this shortcut before a web page can see it, so practice it on the keyboard below. On the real thing, just press the keys together.
Click the modifier keys first (they stay down), then click the final key.