I love that the go team is hostile to breaking stdlib changes (which is what changing the flag package would be). It is so nice to be able to upgrade to the latest go version without having to worry about what it might break in production.

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.