is there a shortcut to lock your macbook?

By most general suggestions, no. Not as simple as windows if computer is to also shut down.

https://duckduckgo.com/?q=how+to+lock+my+macbook+with+keyboard+shortcut&t=ffsb

However you can set it up to require a login password to start, past the login screen; and after

doing that, the shutdown is simple. It won't go past login password screen on wakeup/restart.

This idea has been around awhile, but not as simple as windows OS; an example years old:

http://www.tekrevue.com/tip/the-fastest-way-to-lock-or-sleep-your-screen-in-mac- os-x/

or http://osxdaily.com/2011/01/17/lock-screen-mac/

-- or this, which covers a Mac back-history to pre-OS X:

http://smyck.net/2011/06/02/mac-os-x-keyboard-shortcut-for-locking-the-screen/

These kinds of things changed in time over the evolution of OS X, and I've not used them.

Perhaps someone will post the details (or search Help viewer in OS X) to see what appears.

Maybe advanced users could suggest an script to run from a single click on icon.

Good luck & happy computing! 🙂

Make sure you've set a password for your user account. Then go to System Preferences -> Security & Privacy and set the following options:

To lock your Mac use the key combination SHIFT + FN + CTRL + EJECT.

Alternatively go to System Preferences -> Mission Control -> Hot Corners and define one the four corners of your screen as a go-to-point for the "Put Display to Sleep" function. The system will lock the screen when you move the mouse cursor to that corner.

The shortcuts (among those linked in my reply) also include the workaround

for those computers which had no optical drive and therefore no Eject key.

Good luck in any event...! 😎