Adding Shadows at the bottom of a container in flutter?

I have a simple screen with a container about 100 in height and with blue color. I want to add a shadow or elevation at the bottom of the container.

This is my code below

import 'package:flutter/material.dart';
import 'package:finsec/utils/strings.dart';
import 'package:finsec/utils/dimens.dart';
import 'package:finsec/utils/colors.dart';


void main() {
  runApp(new IncomeFragment());
}

class IncomeFragment extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Stack(
        children: <Widget>[
          new Container(
            height: margin_100dp,
            color: colorPrimary,

          ),
          new Container(    //container to  overlay on top of blue container
            alignment: Alignment.topCenter,


            child: Column(
              crossAxisAlignment: CrossAxisAlignment.center,
              mainAxisSize: MainAxisSize.min,
              children: <Widget>[

                Text(
                    zero_amount,
                    style: TextStyle(color: white, fontSize: 40.0, fontWeight: FontWeight.bold)
                ),
              ],
            ),
          )
        ],
    );
  }
}

can someone help me to add a shadow or elevation at the bottom of my blue container?

see image below. shawdow should be in place in the red circle

thanks in advance

You can reuse the first container that you have in your Stack, the container has a property called decoration and it accept a widget of kind BoxDecoration, as you can see in this link: BoxDecoration Inside this widget you can use the boxShadow property to give to your container a custom shadow, try the next code:

new Container(
      height: margin_100dp,
      decoration: BoxDecoration(
          boxShadow: <BoxShadow>[
            BoxShadow(
                color: Colors.black54,
                blurRadius: 15.0,
                offset: Offset(0.0, 0.75)
            )
          ],
        color: colorPrimary
      ),
    ),