[superjan]

There is a PoC OS in C#.

https://en.wikipedia.org/wiki/Singularity_(operating_system)

[pjmlp]

There are more than one,

https://www.gocosmos.org/

https://www.wildernesslabs.co/

http://joeduffyblog.com/2015/11/03/blogging-about-midori/