>There is unexported code duplicated in the standard library because sharing it would have required exporting those functions: net/http and net/http/httputil share a few parsing functions, and there are four ‘func itoa’ in various packages. Similarly, cmd/nm and cmd/objdump contain the same file reading code.

This is so basic and has been solved by other languages so long ago that it's quite strange to see Go had to reach 1.4, and 5+ years of age to get this...

...and in quite an ad-hoc and hackish way -- which means you're tied to a directory hierarchy.