Google Apps Script to find all members in a group

getGroup.gs

function doGet(e){
  var input = e.parameter.email;
  Logger.log(input);

  if (input == "") 
  {
    return HtmlService.createHtmlOutput("<h2>fail</h2>")
  }
    return HtmlService.createHtmlOutput(listGroupMembers(input))
}; 

function listGroupMembers(input) {
     var group = GroupsApp.getGroupByEmail(input);
     var s = "<div align='center'><font color='fa0029' family='ubuntu'><br><br><b>" + group.getEmail() + '</b><br><br>';
     var users = group.getUsers();
     for (var i = 0; i < users.length; i++) {
       var user = users[i];
       s = s + user.getEmail() + "<br> ";
     }
     s = s + "<br><br><b>Total Users: " + users.length;
     s = s + "<br><button onclick='goBack()'>Go Back</button><script>function goBack() {window.history.back()}</script>";
     Logger.log(s);
     return s;
   }