title: How to get group duration value for group
body: <p>I have a K6 test where load testing a flow and I'm grouping each page request. What I want to do is perform a check on each group's duration so something like </p>
  
  <pre><code>
    group('Home page', function(){
           http.get('localhost:8080')
     });
     //something like this 
     check(group.duration, function()=&gt;{'performs check logic'})
  
     group('search page', function(){
      http.get('localhost:8080/Search?term=mysearch')
     })
     check(group.duration, function()=&gt;{'performs check logic'})
  </code></pre>
  
  <p>The documentation states that group emits group_duration but doesn't state how to listen for it. Not strong in JS so my apologies if this is something simple. </p>