Not to be contrary for its sake, but I'll say this is one change I'm really not happy about. I feel like it's a change to placate many, while driving a lesser amount away. Which is fine, but still feels like the end of something, as I am one of the aforementioned 'lesser.' As for why...I love above most the simplicity and readability of Go. Any change which encroaches that, which this does, is a net negative to me.
Abstractions in libraries? Ok maybe.
In the higher level code that the vast majority of programmers actually write? No. Thank. You.
Besides, interfaces cover the majority of generic problems on the ground.