title: Having trouble posting a child (reply) message to thread in slack channel using the RTM API in google scripts
body: <p>I created a google script linked to a spreadsheet that is designed to send a message to a slack channel thread when a cell is updated. The messages are posting fine to the channel, but I can't get the 'thread_ts' attribute to post the message as a reply to the specific thread as indicated by the timestamp for the parent message. I've read through the documentation several times. What I am doing wrong?</p>
  
  <pre><code>function myonEdit(e) {
  
      var sheet = SpreadsheetApp.getActiveSheet()  
      var range = e.range;
      var columnOfCellEdited = range.getColumn();
  
      if (columnOfCellEdited == 7) {
          var url = "https://hooks.slack.com/services/xxxx/xxxx/xxxx" ;
          var currentRow = sheet.getActiveCell().getRow()
          var name = sheet.getSheetValues(currentRow, 1, 1, 1);
  
          var payload = {
              "username" : "robot", 
              "text" : name,
              "icon_emoji": ":robot_face:",
              "icon_url" : "http://image",
              "thread_ts": "1511829070.000023"
         }
  
      sendToSlack_(url,payload) 
    }
  }
  
     function sendToSlack_(url,payload) {
     var options =  {
         "method" : "post",
         "contentType" : "application/json",
         "payload" : JSON.stringify(payload),
    };
    return  UrlFetchApp.fetch(url, options)
    }
  </code></pre>