Invalid order in SASL authentication call resulting wrong message which trigger connection reset from the server

[yulrizka]

Describe the bug
using Writer struct with SASL authentication resulted sending the wrong message and made the
server terminate the connection

Kafka Version
Azure EventHub

To Reproduce
Create a writer with SASL and TLS using the struct directly

	mechanism := plain.Mechanism{
		Username: "xxx",
		Password: "xxx",
	}


	transport := &kafka.Transport{
		Dial: (&net.Dialer{
			Timeout:   10 * time.Second,
			DualStack: true,
		}).DialContext,
		SASL: mechanism,
		TLS: &tls.Config{
			InsecureSkipVerify: true,
		},
	}
	w := kafka.Writer{
		Addr:        kafka.TCP("someurl.windows.net:9093"),
		Topic:       ActivityLogTopic,
		Balancer:    &kafka.LeastBytes{},
		ErrorLogger: kafka.LoggerFunc(log.Errorf),
		Logger:      kafka.LoggerFunc(log.Infof),
		Async:       false,
		Transport:   transport,
	}

Expected behavior
Not throwing any error

Additional context
I did some debugging and found that SASL handshake was performed before getting all available kafka api version.

I made a PR https://github.com/segmentio/kafka-go/pull/541/files

More specifically, in this code, the order should be reversed (also aligned with the protocol)

kafka-go/transport.go

Lines 1138 to 1158 in cb3dd79

	if g.pool.sasl != nil {
	if err := authenticateSASL(ctx, pc, g.pool.sasl); err != nil {
	return nil, err
	}
	}
	r, err := pc.RoundTrip(new(apiversions.Request))
	if err != nil {
	return nil, err
	}
	res := r.(*apiversions.Response)
	ver := make(map[protocol.ApiKey]int16, len(res.ApiKeys))
	if res.ErrorCode != 0 {
	return nil, fmt.Errorf("negotating API versions with kafka broker at %s: %w", g.addr, Error(res.ErrorCode))
	}
	for _, r := range res.ApiKeys {
	apiKey := protocol.ApiKey(r.ApiKey)
	ver[apiKey] = apiKey.SelectVersion(r.MinVersion, r.MaxVersion)
	}

Since the order was reverse, the handshake was done with emtpy c.versions which resulted in wrong api 0 instead of 1

kafka-go/protocol/conn.go

Lines 81 to 91 in cb3dd79

	func (c *Conn) RoundTrip(msg Message) (Message, error) {
	correlationID := atomic.AddInt32(&c.idgen, +1)
	versions, _ := c.versions.Load().(map[ApiKey]int16)
	apiVersion := versions[msg.ApiKey()]
	if p, _ := msg.(PreparedMessage); p != nil {
	p.Prepare(apiVersion)
	}
	return RoundTrip(c, apiVersion, correlationID, c.clientID, msg)
	}

[achille-roussel]

Thanks for the detailed bug report @yulrizka!

I merged your change and tagged a release for v0.4.6 containing it 👍