Someone please pass this to the Go team, something like this would really be nice to have in the default Go distribution.
Their default argument parsing library is pretty horrible - it uses single-dash for word flags (thus does not differenciate between -h -e -l -p and -help...) and they refuse to implement double-dash, citing "there's third party libs for that".
It really annoys me. I understand the predicament that the stdlib should remain relatively stable, but setting the wrong example in the stdlib itself is really bad - third party libs or not, you know a fair share of people will stick to the stdlib where possible.
I had the exact same experience with python a few days ago. Python's builtin elementtree can't add doctypes at all and is hostile to patches adding it. The reasoning being "lxml exists". For the simple task of adding a doctype, one must either deal with a cpython-specific extension that is a pain in the arse to build, or hack it in with undocumented functionality in minidom.
It is true that the go team is cautious about what goes into the stdlib. Part of that is their commitment to long term support of the standard library. To be able to do that effectively they need to be discerning when choosing what to have there vs an external library. But that doesn't mean that they don't take big changes. HTTP2 support will be in 1.6 which is a huge addition.
Haskell has problem too, where the Prelude (a std lib imorted into programs by default) is designed for learning the language, and getting real work done requrequires supressing the Prelude to work around its bad performance and unsafe semantics.
The golang.com/x/ packages seems to be handling extending the stdlib at this point.
In the case of Go they also prefer to let third parties experiment and determine which design works best rather than trying to guess.
So it's all a bit subjective hence the differing opinions. The point is it's people trying to balance trade-offs.
The Go team comes from an old unix background where long options with a single '-' was standard. GNU changed that, and a good part of the world standardized around it (but not the X11 people for example); now the cultures collide, and people don't understand why the behaviour is different.