Citar is a part-of-speech tagger, based on a trigram Hidden Markov Model (HMM). It (partly) implements the ideas set forth in [1]. It can be used as a set of stand-alone programs and or from Go.
The C++ version of Citar can be found is still available. Active maintenance will proceed in Go. The choice to port Citar from C++ to Go was not made lightly. However, I believe that switching to Go will ease maintenance, lower the barrier for contributions, and improve cross-platform support. Moreover, recent version of Go have made it easier to call Go code from C.
[1] TnT - a statistical part-of-speech tagger, Thorsten Brants, 2000