Similar issue might already be logged but hope this can be a useful test case.
Version: both 1.5.1 and 1.4.3
Example code at http://play.golang.org/p/R9dgBT5joU
time.Now().Format("Fri, 22 Oct 2015 11:52:25 GMT") produces something like
Fri, 1010 Oct 101100 1111:0010:1000 GMT