The Go language is an excellent tool for shipping maintainable server-side applications.
The first answer to this Quora question by one of the developers of D explains a few other points and also what golang is really good at:
https://www.quora.com/Which-language-has-the-brightest-futur...
The type system not being "strong" simply means that you put logic in functions and methods instead of magic parts of the type system.
And Go can absolutely make abstractions. The standard library is full of abstractions. Every Go package is an abstraction. Hell, every function is an abstraction.
And are they easy to maintain?
Because immutability is a massive boon to horizontal scaling and maintainability in ways that are simply unattainable in languages where it's not encouraged. It makes concurrency and parallelism observably trivial, it makes your code safer. Assuming you're using a strictly evaluated (AKA eager, greedy, whatever else you know to mean not-lazy) language with immutable data, race conditions are eliminated.
Let's review that again. In a large distributed codebase written in an immutable language, (let's say Elixir, it's fashionable at the moment and good for doing this kind of stuff) concurrency and parallelism are trivial and race conditions are nonexistent. This is even before we get to type safety and stuff like the actor model. That's huge. That's the immutability advantage. I could go on but it's late and I have school tomorrow.