protocol: `io.MultiReader` stuck on `bufio.Reader.Read(b)`

[pires]

io.MultiReader only advances to the next reader when the current reader returns io.EOF. A bufio.Reader wrapping an open net.Conn will not return EOF when its buffer is empty; it will instead read more data from the underlying connection to refill its buffer. This results in the io.MultiReader to get stuck on the bufio.Reader for the entire lifetime of the connection, which effectively makes the direct conn.Read(b) unreachable dead code.

For more info, see #142 #123 #120 #119