how to give gradint to floating action button in flutter code example

Example: flutter floating action button gradient

floatingActionButton: FloatingActionButton(
          child: Container(
            width: 60,
            height: 60,
            child: Icon(Icons.add),
            decoration: BoxDecoration(
                shape: BoxShape.circle,
                gradient: LinearGradient(colors: [Colors.red, Colors.blue])),
          ),
          onPressed: () {},
        )