how to expose hello hello2 hello3 services on one HelloServer

I have succeeded in compiling 3 different service implementations within one HelloServer via 3 different modules within one library exposing the 3 different implementation, but there is only one serve() function called and not the other two.

How do I specify HelloServer should be ready to serve up the 3 services on the same port number rather than just one?

Thank you for listening.