How to use postinstallpage and configurepage modules in descriptor file?

Hai all,
I am in need to create a third party integration with jira. I chose connect app after lot of discussions. Now i need to develop a postinstallpage and configurepage. I read some documents about these. but didn’t get any clarification. I will explain my requirement. If anyone know about it, kindly give your suggestions.

First i will post my code.

In atlassian-connect.json,

"postInstallPage": {
            "url": "/my-post-install-page",
            "name": {
              "value": "My Post-Install Page",
              "i18n": "mypostinstallpage.name"
            },
            "key": "my-post-install-page"
        },
        "configurePage": {
            "url": "/my-config-page",
            "name": {
              "value": "My Configure Page"
            },
            "key": "configpage"
        }

I added these lines under modules in atlassian-connect.json

In index.js,

app.get('/my-post-install-page', addon.authenticate(), (req, res) => {
      res.render(
        'postinstallpage.hbs', 
        {
          title: 'Atlassian Connect'
        }
      )
    });
  
    app.get('/my-config-page', addon.authenticate(), (req, res) => {
      res.render(
        'configpage.hbs', 
        {
          title: 'Atlassian Connect'
        }
      )
    });

In postinstall.hbs file,

<!doctype html>
<html>
  <head>
    <script id="connect-loader" data-options="sizeToParent:true;">
    (function() {
      var getUrlParam = function (param) {
        var codedParam = (new RegExp(param + '=([^&]*)')).exec(window.location.search)[1];
        return decodeURIComponent(codedParam);
      };

      var baseUrl = getUrlParam('xdm_e') + getUrlParam('cp');
      var options = document.getElementById('connect-loader').getAttribute('data-options');

      var script = document.createElement("script");
      script.src = baseUrl + '/atlassian-connect/all.js';

      if(options) {
        script.setAttribute('data-options', options);
      }

      document.getElementsByTagName("head")[0].appendChild(script);
    })();
    </script>
  </head>
<body>

<h1>An introductory page</h1>

<p>Use this page to show the installer some information on how to use your add-on.</p>
</body>
</html>

When i run this code in my cloud instance, I got the buttons get started and configure.
Now my doubt is when i click the get started or configure button why it will redirect to a page with url “plugins/servlet/ac/app_name/my-config-page” and send 404 error.

Shall i missed anything to do or did i understand wrongly about the flow of using postinstallpage and configurepage? Please give a clarity in this problem.

Thanks in advance…