DStv comes with a satellite signal and Gotv comes with antenna signal, so to connect both cables on one coaxial cable, you’ll need to find a tool that will allows you to send both the satellite and antenna signal to each decoder destination.
The tool you’ll need here is a diplexer, you have to get two diplexers. One diplexer to combine the signal and the other diplexer to split the signal.
The Video Below Illustration How To Install DStv And Gotv On One Cable: