code: func (p *packetPacker) PackConnectionClose(ccf *wire.ConnectionCloseFrame) (*packedPacket, error) {
  	payload := payload{
  		frames: []wire.Frame{ccf},
  		length: ccf.Length(p.version),
  	}
  	encLevel, sealer := p.cryptoSetup.GetSealer()
  	header := p.getHeader(encLevel)
  	return p.writeAndSealPacket(header, payload, encLevel, sealer)
  }
docs: // PackConnectionClose packs a packet that ONLY contains a ConnectionCloseFrame