connect() hangs when server does not respond to pre-login

[datbth]

Describe the bug
When connecting to a server that does not respond to pre-login packets, connect() would hang indefinitely.

To Reproduce

func TestSqlserverConnectTimeout(t *testing.T) {
	sd := sqlserver.Driver{}
	cntor, cntorErr := sd.OpenConnector("sqlserver://128.199.74.51:8000")
	if cntorErr != nil {
		panic(cntorErr)
	}

	ctx, cancelTimeout := context.WithTimeout(context.Background(), 1*time.Second)
	defer cancelTimeout()

	_, connErr := cntor.Connect(ctx)
	assert.ErrorContains(t, connErr, "timeout")
}

Expected behavior
The above test passes (connErr is a timeout error)

Further technical details

I found that it hangs in readPrelogin(), at r.BeginRead()

[datbth]

Setting "connection timeout" would make the connection time out.

But

• I only want to set timeout for the initial Connector.Connect() only. I don't want the timeout to affect the statement/query execution.
• The doc also advises using Context timeout in favor of "connection timeout".