The quality of the standard library, especially net, time, and to a lesser extent, strings.
The tooling, including the built-in testing package and test tool, and go doc. Also vet and fmt, if for no other reason than it precludes most arguments over braces and tabs vs spaces. I don't have cause to use it much, but pprof is a dream.
I like the idea of the go module system, and the fact that dependency management is part of the language ecosystem. It's still a bit clunky, especially if you end up, like I did, stuck with a system that has lots of libraries with poorly-thought out dependency relationships.
interfaces, especially single-method ones. But also the fact that your code doesn't have to declare it's implementing an interface, and has no dependencies on the interface declaration itself.