Figured it out, since Debian repos do not have latest Mono, at least for Debian 9 Stretch, I had to get Mono from the Mono repos, here's how I did it for anyone coming in the future: If you installed Mono already, uninstall it
$ sudo apt-get purge mono-runtime && sudo apt-get autoremove
Install a more recent Mono:
$ sudo apt install dirmngr ca-certificates gnupg
$ apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
$ echo "deb [trusted=yes] https://download.mono-project.com/repo/debian/ stable-stretch main" | sudo tee /etc/apt/sources.list.d/mono-official-stable.list
$ sudo apt update && sudo apt upgrade
$ sudo apt install mono-runtime/stable-stretch