code: public function extendExpiration()
      {
          if (null === $this->ttl) {
              throw new DomainException('There is no TTL set for this Lock.');
          }
  
          if (!$this->expiresAt) {
              $this->expiresAt = new \DateTime();
              $this->expiresAt->setTimestamp(time());
          }
  
          $this->expiresAt->add($this->ttl);
      }
docs: Extend the expiration datetime by the set TTL.
  
  If there is no expiration datetime initialized, it will be.
  
  @throws \DomainException If there is no TTL set.