code: func packRequestContext(chanID uint16, isMultipart bool, seqNum uint16) uint32 {
  	context := uint32(chanID) << 17
  	if isMultipart {
  		context |= 1 << 16
  	}
  	context |= uint32(seqNum)
  	return context
  }
docs: // +------------------+-------------------+-----------------------+
  // | 15b = channel ID | 1b = is multipart | 16b = sequence number |
  // +------------------+-------------------+-----------------------+