Is it possible to disable shadow/overlay on dialog?

I have achieved the result using below code. Trick is barrierColor property in showDialog method which I set white color with opacity value zero and barrier shadow is vanished

AlertDialog alert = AlertDialog(
    backgroundColor: Colors.transparent,
    elevation: 0,
    content: new Row(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Loader(),
      ],
    ),
  );
  showDialog(
    barrierColor: Colors.white.withOpacity(0),
    barrierDismissible: false,
    context: context,
    builder: (BuildContext context) {
      return WillPopScope(
            onWillPop: (){},
          child: alert);
    },
  );

Got it to work! You have to create your own dialog like Widget within the Builder of the showGeneralDialog method along with setting the barrierColor to null:

await showGeneralDialog(
  context: context,
  pageBuilder: (BuildContext buildContext,
      Animation<double> animation,
      Animation<double> secondaryAnimation) {
    return SafeArea(
      child: Builder(builder: (context) {
        return Material(
            color: Colors.transparent,
            child: Align(
                alignment: Alignment.center,
                child: Container(
                    height: 200.0,
                    width: 250.0,
                    color: Colors.white,
                    child:
                        Center(child: Text('Testing')))));
      }),
    );
  },
  barrierDismissible: true,
  barrierLabel: MaterialLocalizations.of(context)
      .modalBarrierDismissLabel,
  barrierColor: null,
  transitionDuration: const Duration(milliseconds: 150));

Friend, set the parameter "elevation" = 0. It's work.

AlertDialog(
 elevation: 0,
),