golang.org/x/net/html-节点的令牌类型

I am using the "golang.org/x/net/html" package and this example to iterate through an html document.

doc, err := html.Parse(r)
if err != nil {
    // ...
}
var f func(*html.Node)
f = func(n *html.Node) {
    if n.Type == html.ElementNode && n.Data == "a" {
        // Do something with n...
    }
    for c := n.FirstChild; c != nil; c = c.NextSibling {
        f(c)
    }
}
f(doc)

Now I want to get the TokenType of each a-element.

How do I get the html.TokenType of a html.Node?