title: How to set ssm param locally for serverless offline
body: <p>I recently starting working on serverless architecture. Here is example of serverless.xml for the same. </p>
  
  <pre><code>test:
      name: test
      handler: handler.lambda_handler
      timeout: 6
      environment:
        APP_ID: ${ssm:/path/to/ssm/test~true}
  </code></pre>
  
  <p>Now when I am trying to run serverless offline command then it complains about ssm variable. 
  Following is the error that coming on console. </p>
  
  <p>I want to run everything on my locally machine for development. Can someone help on this how I can solve this problem. </p>
  
  <pre><code>ServerlessError: Trying to populate non string value into a string for variable ${ssm:/path/to/ssm/test~true}. Please make sure the value of the property is a string.
        at Variables.populateVariable (C:\Users\kumarn\AppData\Roaming\npm\node_modules\serverless\lib\classes\Variables.js:464:13)
        at Variables.renderMatches (C:\Users\kumarn\AppData\Roaming\npm\node_modules\serverless\lib\classes\Variables.js:386:21)
        at C:\Users\kumarn\AppData\Roaming\npm\node_modules\serverless\lib\classes\Variables.js:406:29
    From previous event:
  </code></pre>