Upgrade Go to 1.8.1
Go 1.8 now only supports OS X 10.8 or later. This is likely the last Go release to support 10.8. Compiling Go or running binaries on older OS X versions is untested.
See also #21709 (moved) for Go 1.7.5. I'm going to test a 1.7.5 patch before working on 1.8.