There are also Go koans: https://github.com/cdarwin/go-koans
See also the previous posts of rubykoans:
Coincidentally, we're looking for London based senior, test-driven Ruby devs (contract).
this works though:
Issuer: DigiCert SHA2 High Assurance Server CA
Expires on: 19 mai 2017
Current date: 2 avr. 2015
There are some downsides to this approach that are described there.