We are using 
CarbonAPI and Carbonzipper are Go implementations of a Graphite API server. See
cmd/carbonapi and cmd/carbonzipper for more information on each.
CarbonAPI should now do everything Carbonzipper used to. It's probably the project you're interested in.
This program was originally developed for Booking.com. With approval from Booking.com, the code was generalised and published as Open Source on github, for which the author would like to express his gratitude.
This code is licensed under the BSD-2 license.