title: How to retrieve spanid using java in Sleuth version 2.0.4
body: <p>I need to know the SpandId in java code but I don't know how to get it. I had been searching and I found that many people refer to Tracer class, but it is not available at sleuth 2.0.4.</p>
  <p>Does anybody know how to get the SpandId using sleuth 2.0.4?</p>
  <p>Thanks!</p>