brew install gpg
brew cask install keybase
keybase login $USERNAME
Import your existing GPG key
keybase pgp export | gpg --import
Create a GPG key.
keybase pgp gen --multi
gpg --list-secret-keys --keyid-format LONG
cd $REPOSITORY
git config user.signingkey $KEY_ID
git config commit.gpgsign true
Visit your GitHub keys settings page.
keybase pgp export -q $KEY_ID | pbcopy
Click "New GPG Key" and paste it into the page.