How to retrieve the content (with a specific ID) via ajax by clicking a link tag

I want to retrieve the content with the specific ID via ajax post method.

For instance, if I click a link tag which has a specific post ID, the content of that ID will load into the post-data div.

I am very new to wp ajax and could someone help me to achieve this?

Here is my codes
HTML a tag

<a id="<?php the_ID(); ?>" href="#">This is link</a> 
<!-- the content -->
<div id="post-data"></div>

Jquery Ajax

    $("a").click(function (event) {
    var post_ID = $(this).attr('id');
    $.ajax({
        url: "/wp-admin/admin-ajax.php",
        type: "POST",
        action: "my_custom_data",
        data: {post_link: post_ID},
        success: function (response) {
            console.log(response);
            $('#post-data').append(response);
        }
    });
    event.stopImmediatePropagation();
    event.preventDefault();
    return false;
    });

WP Action

   add_action('wp_ajax_my_custom_data', 'my_custom_data');
   add_action('wp_ajax_nopriv_my_custom_data', 'my_custom_data');

   function my_custom_data(){
   $post_link = data['post_link'];
   echo get_the_content($post_link);
   die();
   }

I think something is wrong with my codes, I just get the response 0.

I would put the action in the post data

$.ajax({
  url: "/wp-admin/admin-ajax.php",
  type:"POST",
       data: { 
       action: "my_custom_data",
       post_link: post_ID
},
success: function (response) {
        console.log(response);
        $('#post-data').append(response);
    }
});
   return false;
.....

Then use $_POST[‘post_link’] in your PHP

   function my_custom_data(){
       $post_link = $_POST['post_link'];
   echo get_the_content($post_link);
   die();
   }