I have done something similar. For a software, which take shared libraries - usually written in C - as plugins, I wrote such a plugin in Go. This was a very good experience. It took only little work to set up the C compatible Go functions realizing the API, but the rest I could implement in Go which made the life so nice. I also ended up calling back into some of the applications APIs from Go, that worked seamlessly.

Go has good facilities interfacing with C, the only attention you need to pay is properly handling C pointers (manual memory management) vs. Go pointers (automatically managed via the GC). But with very little care this is not a big issue. The Go part of the code is however much nicer than if you had to implement the functionality in C. (Yes, I do think that Go is a great C replacement)