title: How to add circular border to dialog in flutter?
body: <p>How to add  circular border for dialog box in a flutter?,I tried the below code but I can't able to get the desired output, I already added circular border but it's not working, I need circular border for dialog,Refer the expected output for details, please guide</p>
  <p>My code :
  `</p>
  <pre><code>class CustomDialog extends StatelessWidget {                                                          
    @override
    Widget build(BuildContext context) {                                                                  
      const double padding = 1.0;                                                                                
      return Dialog(
          backgroundColor: Colors.green,
          shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(8.0),
          ),
          child: Container(
              decoration: BoxDecoration(
                  borderRadius: BorderRadius.all(Radius.circular(20.0))),
              child: Column(mainAxisSize: MainAxisSize.min, children: [
                Container(
                  margin: EdgeInsets.all(1),
                  width: double.infinity,
                  child: Text('title',
                      style: TextStyle(fontSize: 30, color: Colors.white)),
                  color: Colors.green,
                ),
                Container(
                  color: Colors.white,
                  padding: EdgeInsets.all(10),
                  child: ListView(
                    shrinkWrap: true,
                    children: [
                      Container(
                          margin: EdgeInsets.only(left: 10, bottom: 10),
                          height: 30,
                          child: Text('one',
                              style: TextStyle(
                                fontSize: 20,
                              ))),
                      Container(
                          margin: EdgeInsets.only(left: 10, bottom: 10),
                          height: 30,
                          child: Text('one',
                              style: TextStyle(
                                fontSize: 20,
                              ))),
                      Container(
                          margin: EdgeInsets.only(left: 10, bottom: 10),
                          height: 30,
                          child: Text('one',
                              style: TextStyle(
                                fontSize: 20,
                              ))),
                    ],
                  ),
                ),
                Divider(
                  color: Colors.white,
                ),
                Container(
                    color: Colors.white,
                    height: 50,
                    padding: EdgeInsets.all(5),
                    alignment: Alignment.centerRight,
                    child: Text(
                      'CANCEL',
                      style: TextStyle(fontSize: 20),
                    )),
              ])));
    }
  }
  </code></pre>
  <p>`</p>
  <p>My expectation:<a href="https://i.stack.imgur.com/9Y72o.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9Y72o.png" alt="expected output" /></a></p>
  <p>current output:<a href="https://i.stack.imgur.com/52iid.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/52iid.png" alt="my output" /></a></p>