Map function for arrays/slices in Go

How to write a functional Map function in Go using generics. The classical foundation of data pipeline code!

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Map applies a function to each element in the input slice and returns a new slice with the results. The function f takes an element of type A and returns an element of type B.

func Map[A, B any](input []A, f func(A) B) []B {
	result := make([]B, len(input))
	for i, v := range input {
		result[i] = f(v)
	}
	return result
}

and this is a unittest for the function:

func TestMap(t *testing.T) {
	input := []int{1, 2, 3, 4, 5}
	f := func(a int) int {
		return a * 2
	}
	expected := []int{2, 4, 6, 8, 10}
	result := util.Map(input, f)
	if !reflect.DeepEqual(expected, result) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}