We developed a library for oidc federation in the go programming language.
The implementation mainly focuses on the Relying Party side, but can also be utilized for other entity types. The repository also provides example implementations for a Relying Party and an Intermediate Authority / Trust Anchor. Those serve as examples and are not production ready. However, they can serve as a good starting point on how the oidcfed library can be used to implement such entities and also can be used for demonstrations. As such we also have them deployed in our testbed.
The implementation is MIT-licensed and available on Github under: https://github.com/zachmann/go-oidcfed