code: func (api *HandshakeAPI) ReleaseHandshakeKey(pubkeyid string, topic Topic, symkeyid string, flush bool) (removed bool, err error) {
  	removed = api.ctrl.releaseKey(symkeyid, &topic)
  	if removed && flush {
  		api.ctrl.cleanHandshake(pubkeyid, &topic, true, true)
  	}
  	return
  }
docs: // Manually expire the given symkey
  //
  // If `flush` is set, garbage collection will be performed before returning.
  //
  // Returns true on successful removal, false otherwise