How to print the author's post on jekyll

I'm trying to write the post's author when I squeeze the loop to list the posts in the index, but can not do that.

Does anyone have any ideas?

Follow the code:

{% for post in site.posts %}    
    {% assign author = site.authors[post.author] %}
    {{author.name}} // não printa nada aqui 
{% endfor %}

_config.yml:

authors:
  bruno_folle:
    name: Bruno Folle

front matter:

---
layout: post
title:  "Welcome to Jekyll!"
date:   2018-09-17 12:58:34 +0200
categories: jekyll update
author: bruno_folle
---