How to pass "extra arguments" to handlers in Go

extraarghandler.go

type HandlerData struct {
    data string
    //whatever
}

func main(){
	//Create a data struct
        // add data to struct
        h := &HandlerData{...}

	http.Handle("/foo", http.HandlerFunc(h.Handle))
}

func (h *HandlerData) Handle(w. http.ResponseWriter, req *http.Request){
	//data that was initilized here to be used...
        w.Write(h.data) //Data has been json and marshalled
	return
}