macOS Sierra instructions?

[JoeMurray]

I'm getting an error in Chrome on my mac indicating an installation issue. I click on the message and go to http://leoiannacone.github.io/goopg/

The problem is that from a terminal on a mac following those instructions yields:
$ sudo apt-add-repository ppa:team-goopg/goopg
Password:
sudo: apt-add-repository: command not found
$

Could you provide instructions for macOS, or a link to them? Thx

[LeoIannacone]

Try this https://github.com/LeoIannacone/goopg/blob/master/doc/mac-install.md