code: func UpdateArticle(w http.ResponseWriter, r *http.Request) {
  	article := r.Context().Value("article").(*Article)
  
  	data := &ArticleRequest{Article: article}
  	if err := render.Bind(r, data); err != nil {
  		render.Render(w, r, ErrInvalidRequest(err))
  		return
  	}
  	article = data.Article
  	dbUpdateArticle(article.ID, article)
  
  	render.Render(w, r, NewArticleResponse(article))
  }
docs: // UpdateArticle updates an existing Article in our persistent store.