Flutter error "Multiple widgets used the same GlobalKey" - using ScreenShot with SocialShare plugins

I'm not sure where to find the extra widget sharing the same global key as another widget in my app. I'm using the Screenshot and Social Share plugins.

https://pub.dev/packages/screenshot

https://pub.dev/packages/social_share

I'd like to upload a screenshot when sharing to social media such as Facebook Messenger. But I'm getting the following error in my console which occurred only after I added the screenshot controller;

Flutter Multiple widgets used the same GlobalKey

Where am I getting this problem? I created the screenshot instance within the state;

class _StageBuilderState extends State<StageBuilder> {
    ScreenshotController screenshotController = ScreenshotController();

Here's the build;

Widget createViewItem() {
    return Screenshot(
    controller: screenshotController,
          Column(
             children: <Widget>[
              child: Image.network( myavatar),
              child: IconButton(
                 icon: Icon(Icons.share),
                onPressed: () async {
                   await screenshotController.capture().then((image) async {
                   SocialShare.shareOptions("http://myurl", imagePath: image.path);
                      }
                   );
                 },
              ),
          ],
       ),
    ),
}

So where's this extra widget sharing the same global key as something else in my app? Where should I start troubleshooting?

Turns out I had to make the Screenshot controller local and put it here;

Widget createViewItem() {
   ScreenshotController _screenshotController = ScreenshotController();
    return Screenshot(
    controller: screenshotController,
          Column(
             children: <Widget>[
              child: Image.network( myavatar),
              child: IconButton(
                 icon: Icon(Icons.share),
                onPressed: () async {
                   await screenshotController.capture().then((image) async {
                   SocialShare.shareOptions("http://myurl", imagePath: image.path);
                      }
                   );
                 },
              ),
          ],
       ),
    ),
}