title: Fetch and store data from multiple url for the sections data of SectionList
body: <p>I would like to use the <code>SectionList</code> in react native. </p>
  
  <pre><code>export default class Home extends React.Component {
      constructor(props) {
          super(props);
          this.state = {
              dataSource: [
                  {
                      title: 'New List', data: []
                  },
                  {
                      title: 'Old list', data: []
                  },
              ]
          }
      }
  
      render() {
          return (
              &lt;SectionList
                  style={styles.SectionContainer}
                  sections={this.state.dataSource}
                  renderSectionHeader={this._renderSectionHeader}
                  renderItem={this._renderItem}
                  keyExtractor={(item) =&gt; item.id}
              /&gt;
          )
      }
  }
  </code></pre>
  
  <p>Each section's data can be fetched by separate url, and they basically have the same json data:</p>
  
  <pre><code>getNewList() {
      const url = website + '/api/new-list/';
      return fetch(url)
          .then((res) =&gt; res.json())
          .catch((err) =&gt; console.log(err))
  },
  
  getOldList() {
      const url = website + '/api/old-list/';
      return fetch(url)
          .then((res) =&gt; res.json())
          .catch((err) =&gt; console.log(err))
  }
  </code></pre>
  
  <p>How can fetch and store both the response data for the <code>dataSource</code> of <code>SectionList</code>?</p>