Using impl to create an implementation of the sort interface

impl_sort.go

// Len is the number of elements in the collection.
func (Foo) Len() int {
	panic("not implemented") // TODO: Implement
}

// Less reports whether the element with
// index i should sort before the element with index j.
func (Foo) Less(i int, j int) bool {
	panic("not implemented") // TODO: Implement
}

// Swap swaps the elements with indexes i and j.
func (Foo) Swap(i int, j int) {
	panic("not implemented") // TODO: Implement
}