My understanding is that the original C toolchain in Go (only recently removed in 1.5) was based heavily on the Plan 9 compilers.

In fact there was a rather inflammatory blog post[1] whose basic theme was that "Golang is trash" because the toolchain was so simple. One of the main Go developers then responded[2] on HN. Different people value different things I suppose.

1. http://dtrace.org/blogs/wesolows/2014/12/29/golang-is-trash/

2. https://news.ycombinator.com/item?id=8817990

I've hacked heavily with both; I've even compiled the Plan 9 kernel using Go's compiler+linker. The compilers are damn good. I went from no knowledge of 6[cl] (the amd64 compiler&linker) to pretty comfortable with the source in about 2 days.

Go uses customized but recognizable derivatives of the Plan 9 compilers. Go's compilers are really only intended to compile the Go tools, so you might find it painful to build anything else.

Getting 6c/6l/6a compiled on Linux would be easier these days because gcc's -fplan9-extensions flag will bring you pretty close... check out https://github.com/rminnich/NxM/tree/master/util for the source and scripts to build them on Linux. I believe you can make it output elf binaries but I've never tried using them to build a Linux program.