code: public ServerBuilder idleTimeout(Duration idleTimeout) {
          requireNonNull(idleTimeout, "idleTimeout");
          idleTimeoutMillis = ServerConfig.validateIdleTimeoutMillis(idleTimeout.toMillis());
          return this;
      }
docs: Sets the idle timeout of a connection for keep-alive.
  
  @param idleTimeout the timeout. {@code 0} disables the timeout.