Anonymous functions aren't the same as lambda functions. People in the Go community keep asking for lambda functions and never get them. There should be no need for func/fn and explicit return. Because the arrow would break stuff is one of the reasons.

See

https://github.com/golang/go/issues/59122

https://github.com/golang/go/issues/21498

    res := is.Map(func(i int)int{return i+1}).Filter(func(i int) bool { return i % 2 == 0 }).
             Reduce(func(a, b int) int { return a + b })

    res := is.Map((i) => i+1).Filter((i)=>i % 2 == 0).Reduce((a,b)=>a+b)