code: func (h *hawkularSink) pushToCache(key string, hash uint64) {
  	h.regLock.Lock()
  	h.expReg[key] = &expiringItem{
  		hash: hash,
  		ttl:  h.runId,
  	}
  	h.regLock.Unlock()
  }
docs: // toCache inserts the item and updates the TTL in the cache to current time