title: Use Jenkins WORKSPACE environment variable in Jenkins declarative pipeline parameter
body: <p>Is there a way to use Jenkins WORKSPACE environment variable in Jenkins declarative pipeline parameters?</p>
  <p>Below attempt failed.</p>
  <pre><code>pipeline {
      parameters {
          extendedChoice description: 'Template in project',
                          multiSelectDelimiter: ',', name: 'TEMPLATE',
                          propertyFile:  env.WORKSPACE + '/templates.properties', 
                          quoteValue: false, saveJSONParameterToFile: false, type: 'PT_MULTI_LEVEL_SINGLE_SELECT',
                          value: 'Project,Template', visibleItemCount: 6
     ...
     } 
     stages { 
     ...
     }
  </code></pre>
  <p><code>propertyFile: '${WORKSPACE}/templates.properties'</code> didn't work either.</p>