title: Best way to set reusable property in Jenkinsfile
body: <p>My Jenkins pipeline shared library can send notification on demand. The user basically has to send the the notifcation channel details like slack channel name or email id for each stage that he wants notifcation.</p>
  
  <p>I do not want user to repeat this property in every stage but rather define it once in Jenkinsfile and I can use that. What would be the best way to set this variable?</p>
  
  <p>Sample:</p>
  
  <pre><code>// this properties needs to be accessed by my groovy files
  def properties = "channelNm,token"
  node('myNode'){
  
  stage('checkout'){
     slackNotify = "yes"
     .....
   }
   stage('compile'){
     slackNotify = "yes"
     .....
   }
  }
  </code></pre>