I've mostly moved on to Clojure for programming backend services. I still use Go for the occasional small utility program due to its speed and ease of deployment, though.
I've never once even considered the fact that I might need generics because I've never run into an unsolvable problem or an extremely inelegant engineering solution. I see a lot of people claiming that the lack of generics is a big problem but no one is actually showing a concrete case where generics are necessary.
C doesn't have generics but we never have this discussion when we talk about C.
That is a trivial example where generics help. And yes, the endless boxing and runtime type assertion does make your code slower eventually (see the comment from the libcuckoo authors).
This is one of the reasons why the container and sort stdlb libraries are such a joke. They're not generic so they have to special case every different type. With generics, the entire sort package would just be a function that takes Ordinal and sorts it. Container would similarly only require one implementation of each data structure (because they would be generic).
I find it hard to believe that you've programmed "scores of Go" and you've never hit any of these issues. I also have programmed plenty of Go, and these problems are just frustrating.
But again, I still severely doubt you've never run into a problem with Go's lack of generics. I ran into it after about 3 months of working with Go. Maybe you didn't find the work-arounds problematic, but that doesn't mean that the original limitation (no generics) doesn't cause problems. You just choose to accept the work-arounds as the "right way" of doing things.
If you haven't already, I would recommend looking at Rust or another modern language that has generics to see what sort of benefits you can get out of it that you can't directly get with Go. Personally the fact that if T implements an interface I won't let you use T as I is pretty silly IMO. Rust lets you do that with the From trait, and you can even do it even more generically with the From trait using a generic T.
Sure it does, a light weight version was introduced in C11.
Besides, C gets an excuse because the language was designed before generics were even invented, and with pre-processor macros is it possible to implement a poor man's generic system.