I dit it 
(I have a server on Ubuntu 16.04)
Download on your server :
- https://download.mono-project.com/sources/mono/mono-4.8.1.0.tar.bz2
- tar xvjf mono-4.8.1.0.tar.bz2
- cd mono-4.8.1
- ./configure
- make
- sudo make install
(Don’t forget to apt-get upgrade & apt-get update)
And it’s work