code: func (f *ConnectionCloseFrame) Length(version protocol.VersionNumber) protocol.ByteCount {
  	length := 1 + 2 + utils.VarIntLen(uint64(len(f.ReasonPhrase))) + protocol.ByteCount(len(f.ReasonPhrase))
  	if !f.IsApplicationError {
  		length++ // for the frame type
  	}
  	return length
  }
docs: // Length of a written frame