Please make sure that you have added the X2Go repository appropriate for your system to your package management system. The required steps are described here:
The x2godesktopsharing package will install x2godesktopsharing on your GNU/Linux system and will make sure, that every needed package will be installed as a dependency. x2godesktopsharing is an X2Go server-side package.
$ aptitude install x2godesktopsharing
You can now start x2godesktopsharing within X2Go sessions (that is: on the server) by typing x2godesktopsharing on the command line or you find it inside the “Internet” section of your menu inside your graphical desktop environment. (In case of LXDE on Debian/Raspbian have a look in 'Networking' instead.)
The sources of this X2Go component are available as source tarball under this URL:
http://code.x2go.org/releases/source/x2godesktopsharing
The X2Go Desktop Sharing tool can be built using qmake-qt4.