title: BorderSide Color to BottomNavigationBar?
body: <p>I want to add a colored BorderSide to the top of my BottomNavigationBar.</p>
  
  <p>I can achieve it using a Custom BottomAppBar, but it is not convenient for my design as it misplaces my floatingActionButtonLocation.centerDocked, so I need to stick with BottomNavigationBar.</p>
  
  <p>Any help to find a workaround is appreciated.</p>
  
  <pre><code>import 'package:flutter/material.dart';
  
  class BottomNavTest extends StatefulWidget {
    @override
    _BottomNavTestState createState() =&gt; _BottomNavTestState();
  }
  
  class _BottomNavTestState extends State&lt;BottomNavTest&gt; {
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        backgroundColor: Colors.grey,
        bottomNavigationBar: BottomNavigationBar(
          type: BottomNavigationBarType.fixed,
          backgroundColor: Colors.grey,
          selectedItemColor: Colors.white,
          unselectedItemColor: Colors.black, //
          currentIndex: 0,
          onTap: (index) {
            switch (index) {
              case 0:
                break;
              case 1:
                break;
            }
          },
          items: [
            BottomNavigationBarItem(
              icon: Icon(Icons.thumb_up),
              title: Text('good'),
            ),
            BottomNavigationBarItem(
              icon: Icon(Icons.thumb_down),
              title: Text('bad'),
            ),
          ],
        ),
      );
    }
  }
  </code></pre>
  
  <p>Current output:</p>
  
  <p><a href="https://i.stack.imgur.com/4jUe1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4jUe1.png" alt="Current Output"></a></p>
  
  <p>My goal:</p>
  
  <p><a href="https://i.stack.imgur.com/D4bpP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/D4bpP.png" alt="My Goal"></a></p>