xdotool Error: Can't open display: (null)

Question

"xdotool key" gives me the following error :

Error: Can't open display: (null)
Failed creating new xdo instance

I downloaded:

  brew cask install xquartz
  brew install xdotool

I added to zshrc file and saved with "source ~/.zshrc":

export DISPLAY=:0

I tried exporting display but none seems to work.

export DISPLAY=:0.0 && xdotool key 'a'

*Im using mac

Any idea ?

Thanks.