Can't use go-tigertonic on Google AppEngine

[przmv]

Hello,

It seems that tigertonic's dependency — go-metrics ain't compile on GAE. I get the following error message when I try deploy tigertonic-based application on appengine:

…
06:11 PM Error 422: --- begin server output ---
Compile failed:
2014/07/23 07:11:56 go-app-builder: build timing: 4×6g (414.00874ms total), 6×gopack (228.451024ms total), 0×6l (0 total)
2014/07/23 07:11:56 go-app-builder: failed running 6g: exit status 1

github.com/rcrowley/go-metrics/runtime.go:122: undefined: runtime.NumCgoCall
--- end server output ---
06:11 PM Rolling back the update.
Error 422: --- begin server output ---

--- end server output ---
error while running appcfg.py: exit status 1

[rcrowley]

Tracking in rcrowley/go-metrics#67. Thanks!