title: How to work with variables in Cloudformation template as the feature of "Data source" in terraform
body: <p>In terraform, we can use <a href="https://www.terraform.io/docs/configuration/data-sources.html" rel="nofollow noreferrer">data source</a> to get the exist resource details. </p>
  
  <p>But in cloudformation, <strong>if the resource isn't created by cloudformation template</strong>, I can't find any ways to reference it, unless I hard code the value, such as real vpc id. </p>
  
  <p>Any suggestions?</p>