title: How can I resolve "Warning: Encountered two children with the same key" on React.js
body: <p>I'm trying to consume the data from an api, but when I try to render the data, I get this error:</p>
  
  <blockquote>
    <p>Warning: Encountered two children with the same key, <code>[object Object]</code>. Keys should be unique so that components maintain their identity across updates. Non-unique keys may cause children to be duplicated and/or omitted — the behavior is unsupported and could change in a future version.</p>
  </blockquote>
  
  <p>Here is a prototype in <a href="https://codesandbox.io/s/zxwpr07jvp" rel="nofollow noreferrer">CodeSandbox</a> ... Probably it's a simple thing to solve, but I started to study the react a few days ago. Can you help me?</p>