code: func NukeCookie(w http.ResponseWriter, r *http.Request, name, path string) {
  	parts := strings.Split(missinggo.SplitHostMaybePort(r.Host).Host, ".")
  	for i := range iter.N(len(parts) + 1) { // Include the empty domain.
  		http.SetCookie(w, &http.Cookie{
  			Name:   name,
  			MaxAge: -1,
  			Path:   path,
  			Domain: strings.Join(parts[i:], "."),
  		})
  	}
  }
docs: // Clears the named cookie for every domain that leads to the current one.