how to add border raduis flutter button code example

Example 1: flutter button border radius

shape: RoundedRectangleBorder(
  borderRadius: BorderRadius.circular(18.0),
  side: BorderSide(color: Colors.red)
),

Example 2: border at circleAvatar flutter

CircleAvatar(
    radius: 30,
    backgroundColor: Colors.teal,
    child: CircleAvatar(
      backgroundImage: AssetImage('assets/appdev.png'),
      radius: 28,
    ),
  ),