How to write foldr and foldl in go?

Question

go

In the exercise task, it was necessary to implement convolution functions . In the description of the assignment, it was written about functional programming, after which I had doubts about the correctness of my decision. Well, i.e. my solution tests pass, but I do it in a loop. Is there any more correct - functional way to solve this problem?

// Fold list from the right
func (l *IntList) Foldr(fn binFunc, init int) (answer int) {
    answer = init
    for i := l.Length() - 1; i >= 0; i— {
        answer = fn((*l)[i], answer)
    }
    return
}
// Fold list from the left
func (l *IntList) Foldl(fn binFunc, init int) (answer int) {
    answer = init
    for i := 0; i < l.Length(); i++ {
        answer = fn(answer, (*l)[i])
    }
    return
}

PS - Just started reading the book Learning Functional Programming in Go