docs: public SyncLazyFuture<X> withRunningThread() {
          if (state != null) return this;
          Thread thread = new Thread(SyncLazyFuture.this.getClass().getName() + ".withRunningThread") {
              @Override
              public void run() {
                  try {
                      SyncLazyFuture.this.internalCalc();
                  } catch (ExecutionException | InterruptedException e) {
                      e.printStackTrace();
                  }
              }
          };
          thread.start();
          return this;
      }