> In my experience all 3 can be written in a really well maintainable way.
That's true, but that is generally true of any (non-toy) language. But in the modern world of rapid development, it matters how hard is it to write code in a non-maintainable way - i.e. how well it tolerates modifications by different people. And to me, it seems easier to write readable code in Go than it is to write unreadable code.
It seems to come from the lack of features - Java, Python and C# have too many features, and any problem can be solved in N different ways, each one with its own warts. If you want to work on a wide range of codebases, you have to know each one of the approaches and their warts and footguns.
Meanwhile, Go feels like it really reached the "there should be one obvious way to do it" ideal of Python, while Python has over the years evolved into something more Perl-like. Want to build a concurrent application? Chose your tradeoff - either you get CPU scalability (multiprocessing) but lose memory sharing, or you get a simple concurrent model (threading) that isn't scalable, or you get I/O scalability (asyncio) at the cost of function coloring, error-proneness and a single-threadedness. Go solved the whole thing with the goroutine model - internally it multiplexes coroutines onto a set of OS threads, but all blocking calls are wrapped by Go runtime which makes every coroutine behave and feel like an ordinary thread, without the massive memory use of OS threads.
The number of ways to write something is only very loosely correlated with maintainability. The ease of maintenance is IMHO more a function of how much information about the properties of the code you can easily read from the text, and how well the abstractions in the code map to the abstractions you'd use when describing the solution to a friend. Lack of features doesn't help in that regard. That's why probably Go has just added generics, despite the long tradition of Go promoters claiming "lack of generics is a good thing" ;)
Languages with very little type information, e.g. dynamic ones, tend to be quite hard to maintain, unless the original developers kept the discipline of good naming and verbose commenting. Go and Java with their somewhat static, but limited typing and elements of dynamism (interface{}, Object, reflection), sit somewhere in the middle between PHP/JS and Rust/Scala/Haskell.
Languages with little expressive / abstraction power, so the ones limited in features or low-level are also often hard to maintain, because you have to reverse-engineer the high-level stuff from all the details you see. Take assembly as an example - while it may be quite obvious what the program is doing at the bits and bytes level, understanding the sense of that bit-level manipulation may be a much harder task. The assembly language might actually be very simple, but that does not help. I remember when we had a MIPS class, the whole specs was just a few pages, could be learned in an hour.
Could you expand a bit on why do you think Java has too many features? It is a very small language, that is often berated because it picks up features way too slowly if anything.
I would go as far to claim that Java is an easier language than Go, or at least in the same ballpark.
> Could you expand a bit on why do you think Java has too many features?
I think you're asking for technical details, but I'm afraid I don't know Java well enough to do an objective comparison. I'll try with a subjective explanation or why I think so.
I've learned Go in 20 minutes following the Go Tour. Few months later, I feel like there isn't a single thing I don't know about Go. It's dead simple. When I open a Go repository, it's easy for me to get into the codebase, as all code is more-or-less the same.
I've learned Java back in high school, and to this day I don't feel like I "know" the language. I've tried reading some Java repositories, and every time I feel like there's some kind of friction - some implicit knowledge about it that I just don't understand.
Maybe it's just me, and I haven't spent enough time learning Java. But then again, I've spent even less time learning Go, and yet I have a much easier time using it. That's what I mean by "a very small language".
That's true, but that is generally true of any (non-toy) language. But in the modern world of rapid development, it matters how hard is it to write code in a non-maintainable way - i.e. how well it tolerates modifications by different people. And to me, it seems easier to write readable code in Go than it is to write unreadable code.
It seems to come from the lack of features - Java, Python and C# have too many features, and any problem can be solved in N different ways, each one with its own warts. If you want to work on a wide range of codebases, you have to know each one of the approaches and their warts and footguns.
Meanwhile, Go feels like it really reached the "there should be one obvious way to do it" ideal of Python, while Python has over the years evolved into something more Perl-like. Want to build a concurrent application? Chose your tradeoff - either you get CPU scalability (multiprocessing) but lose memory sharing, or you get a simple concurrent model (threading) that isn't scalable, or you get I/O scalability (asyncio) at the cost of function coloring, error-proneness and a single-threadedness. Go solved the whole thing with the goroutine model - internally it multiplexes coroutines onto a set of OS threads, but all blocking calls are wrapped by Go runtime which makes every coroutine behave and feel like an ordinary thread, without the massive memory use of OS threads.