I've managed to get Go running on an RPi2 using a similar method, but:
1. You need to make sure you're using go-tip. <= 1.6 doesn't have Plan9/arm support.
2. I had to apply this patch that Richard Miller sent me to my kernel:
term% diff /n/sources/contrib/miller/9/bcm/mem.h /sys/src/9/bcm/mem.h
55c55
< #define USTKTOP 0x20000000 /* user segment end +1 */
---
> #define USTKTOP 0x40000000 /* user segment end +1 */
(Then realized that the git client I was writing in Go wasn't ready enough to use
as a daily driver for developing Go programs under Plan9, so I didn't go much
further than that and compiling a few test programs..)
-- Dave