If you have a []T and you want to apply a function to make it into []K, you need to explicitly make a loop in every case. You might not think that's that bad, but note that T and K could also be interfaces such that T is a superset of K. In that case Go, T can be used as K but []T cannot be used as []K (meaning you have to do an explicit loop for something that should be an implicit type conversion).
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.
If that's true then you might not benefit from generics directly. But you will benefit from having an ecosystem of libraries that take advantage of generics. And even if you don't use other people's libraries, not everyone in the world happens to be as lucky as you and they do need generics to make their lives easier.
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.
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.