code: func (cn *conn) send(m *writeBuf) {
  	b := (*m)[1:]
  	binary.BigEndian.PutUint32(b, uint32(len(b)))
  
  	if (*m)[0] == 0 {
  		*m = b
  	}
  
  	_, err := cn.c.Write(*m)
  	if err != nil {
  		panic(err)
  	}
  }
docs: // Assumes len(*m) is > 5