code: public Stopwatch timer(final Stat name) {
          final Stopwatch watch = timers.computeIfAbsent(name, k -> Stopwatch.createUnstarted());
          // if watch was performed before then new time will sum with current
          watch.start();
          return watch;
      }
docs: If measured first time, returns new instance. For second and following measures returns the same instance
  (to sum measurements).
  Assumed proper usage: timer stat provided and returned watch correctly stopped.
  
  @param name statistic name
  @return timer to measure time