func main() {
    //..

    // find all <li> elements
    var processAllPokemon func(*html.Node)
    processAllPokemon = func(n *html.Node) {
        if n.Type == html.ElementNode && n.Data == "li" {
            // process the Pokemon details within each <li> element
            processNode(n)

        }
        // traverse the child nodes
        for c := n.FirstChild; c != nil; c = c.NextSibling {
            processAllPokemon(c)
        }
    }
    // make a recursive call to your function
    processAllPokemon(doc)
}