From what I understood, MIPS32 support for Golang has been in the pipeline for some time already so it might appear at some point. MIPS64 is there since 1.6 and fully supported in 1.7.
Sadly, very few OpenWRT hardware uses MIPS64, only the higher grade products do.
You will have to use gccgo anyways as long as it is not supported, from what I understand.
Apart from Go compatibility, I can still comment on the board itself: It works well, easy to setup and has good software support from Mediatek, the form factor is an important selling point as well. It is also fully documented and open source hardware.