code: public ServerBuilder gracefulShutdownTimeout(Duration quietPeriod, Duration timeout) {
          requireNonNull(quietPeriod, "quietPeriod");
          requireNonNull(timeout, "timeout");
          gracefulShutdownQuietPeriod = validateNonNegative(quietPeriod, "quietPeriod");
          gracefulShutdownTimeout = validateNonNegative(timeout, "timeout");
          ServerConfig.validateGreaterThanOrEqual(gracefulShutdownTimeout, "quietPeriod",
                                                  gracefulShutdownQuietPeriod, "timeout");
          return this;
      }
docs: Sets the amount of time to wait after calling {@link Server#stop()} for
  requests to go away before actually shutting down.
  
  @param quietPeriod the number of milliseconds to wait for active
  requests to go end before shutting down. {@link Duration#ZERO} means
  the server will stop right away without waiting.
  @param timeout the number of milliseconds to wait before shutting
  down the server regardless of active requests. This should be set to
  a time greater than {@code quietPeriod} to ensure the server shuts
  down even if there is a stuck request.