Attempting to browse to a godoc hosted webpage gives this error: 2015/06/02 19:36:41 lstat /usr/lib/go/favicon.ico: no such file or directory the file is installed by the ebuild. I manually ran ebuild dev-go/go-tools compile, then find /var/tmp/portage *\.ico, which found: /var/tmp/portage/dev-go/go-tools-1.4.2_p20150520/work/src/golang.org/x/tools/cmd/present/static/favicon.ico copying that file to /usr/lib/go/favicon.ico and reloading the page in Chromium then shows the favicon.
I'll see about making it look for the file where it is installed as '/usr/lib/go/src/golang.org/x/tools/cmd/present/static/favicon.ico'.
This is fixed in go-tools-1.4.2_p20150520-r1. The favicon is compiled into godoc along with the other static content.