/usr/lib/go-1.6/favicon.ico is in golang-1.6-doc 1.6.1-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/go-1.6/../../share/doc/golang-1.6-doc/favicon.ico
/usr/lib/go-1.6/../../share/doc/golang-1.6-doc/favicon.ico