the_fix_for_render_flex_children_have_non_zero_flex.dart

void main() {
    runApp(
        Column(
            mainAxisSize: MainAxisSize.min,
            children: <Widget>[
                Flexible(
                    fit: FlexFit.loose,
                    child: Container(
                        color: Colors.blue,
                        height: 100,
                        width: 100,
                    ),
                ),
            ],
        ),
    );
}