code: public void connectRTM(String slackToken) {
          RTM rtm = restTemplate.getForEntity(slackApiEndpoints.getRtmConnectApi(), RTM.class, slackToken).getBody();
          currentUser = rtm.getSelf();
          webSocketUrl = rtm.getUrl();
          getImChannels(slackToken, 200,"");
      }
docs: Start a RTM connection. Fetch the web socket url to connect to, current user details
  and list of channel ids where the current user has had conversation.
  
  @param slackToken slack token which you get from slack for the integration you create