This is not a solution but a work-around: create two projects, one C# Monogame project and one F# console application. Both of these templates should be installed with Xamarin and Monogame.
- Create a C# Monogame project
- Create an F# console application
- Edit the
fsproj
file so that it has OutputType
Library
- Link the F# project to the Monogame project
- Add the Monogame package to the F# library using nuget
- Write your
Game
class in F#!
Aside from the hassle of creating two projects, the main problem I've found is that every reference used in the F# library also needs to be referenced in the C# library or you will get runtime errors. I'm sure a custom build script could be written to fix this.