code: func insert(q *waitForPriorityQueue, knownEntries map[t]*waitFor, entry *waitFor) {
  	// if the entry already exists, update the time only if it would cause the item to be queued sooner
  	existing, exists := knownEntries[entry.data]
  	if exists {
  		if existing.readyAt.After(entry.readyAt) {
  			existing.readyAt = entry.readyAt
  			heap.Fix(q, existing.index)
  		}
  
  		return
  	}
  
  	heap.Push(q, entry)
  	knownEntries[entry.data] = entry
  }
docs: // insert adds the entry to the priority queue, or updates the readyAt if it already exists in the queue