title: Error: No AWSAccessKey was presented - flutter Amplify
body: <p>I have a code like this in my flutter project:</p>
  <pre class="lang-dart prettyprint-override"><code>final imageUrl = await Amplify.Storage.getUrl(key: urlKey);
  
  return StreamBuilder(
  stream: imageUrl.url,
  builder: (context, snapshot) {
  
  if (snapshot.hasData) {
  
  if (snapshot.data.length != 0) {
  return GridView.builder(
  gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
  crossAxisCount: 1),
  itemCount: snapshot.data.length,
  itemBuilder: (context, index) {
      return CachedNetworkImage(
                imageUrl: snapshot.data,
                fit: BoxFit.cover,
                placeholder: (context, url) =&gt; Container(
                  alignment: Alignment.center,
                  child: CircularProgressIndicator(),
                ),
              );
            });
      } else {
        // 5
        return Center(child: Text('No images to display.'));
      }
    } else {
      // 6
      return Center(child: CircularProgressIndicator());
    }
  });
  </code></pre>