title: AWS CloudFormation, refer parameters in tags
body: <p>I am trying to apply a set of tags to a SNS topic and one of the tags refer to a parameter.  Given below is an extract of the template I have (I have reduced the tags to highlight my problem)</p>
  
  <pre class="lang-yaml prettyprint-override"><code>AWSTemplateFormatVersion: 2010-09-09
  Description: Deploys resources 
  
  Parameters:
    MyParameter:
      Type: String
      Default: "testEnvironment"
  
  Mappings:
    Mp1:
      Mp1-1:
        tags:
          - Key: key1
            Value: !Ref MyParameter
  
  Resources:
    snsTopic:
      Type: AWS::SNS::Topic
      Properties:
        DisplayName: snsTopic
        TopicName: snsTopic
        Tags: !FindInMap [Mp1, Mp1-1, tags]
  </code></pre>
  
  <p>Now when I run this on CloudFormation I get the following error:</p>
  
  <p><code>Every entry in list for property Tags must be a map of String</code></p>
  
  <p>Does someone know how to fix this or what I am doing wrong?</p>