If you were being formal, you would say "Goober sends his regards." If you were being informal, you would say "Goober says hello." If you live in the American South, you would say "Goober says 'hey'".
Unless you are talking to a head of state or corporate executive, it's more common to say "I just saw Goober the other day, and he aked me to say "hello".) Similarly, if you're passing along a message, you'd say something along the lines of:
"Goober wanted me to tell you...."
"Goober asked me to mention...."
