## listsize

### Instructions

Write a function `ListSize` that returns the number of elements in a linked list `l`.

### Expected function and structure

```go
type NodeL struct {
	Data interface{}
	Next *NodeL
}

type List struct {
	Head *NodeL
	Tail *NodeL
}

func ListSize(l *List) int {

}
```

### Usage

Here is a possible program to test your function :

```go
package main

import "fmt"

func ListPushFront(l *List, data interface{}) {
	n := &NodeL{Data: data}
	if l.Head == nil {
		l.Head = n
		l.Tail = n
	} else {
		l.Head, n.Next = n, l.Head
	}
}

func main() {
	link := &List{}

	ListPushFront(link, "Hello")
	ListPushFront(link, "2")
	ListPushFront(link, "you")
	ListPushFront(link, "man")

	fmt.Println(ListSize(link))
}
```

And its output :

```console
$ go run .
4
$
```