Readd dial timeout error code and a test

This was dropped as part of #2008 but it will be better if we
differentiate between different timeouts

Also add test for the `request timeout` error code in `httpext`

lib/netext/httpext/error_codes.go

@@ -57,6 +57,7 @@ const (
 	tcpBrokenPipeErrorCode   errCode = 1201
 	netUnknownErrnoErrorCode errCode = 1202
 	tcpDialErrorCode         errCode = 1210
+	tcpDialTimeoutErrorCode  errCode = 1211
 	tcpDialRefusedErrorCode  errCode = 1212
 	tcpDialUnknownErrnoCode  errCode = 1213
 	tcpResetByPeerErrorCode  errCode = 1220
@@ -86,6 +87,7 @@ const (
 
 const (
 	tcpResetByPeerErrorCodeMsg  = "%s: connection reset by peer"
+	tcpDialTimeoutErrorCodeMsg  = "dial: i/o timeout"
 	tcpDialRefusedErrorCodeMsg  = "dial: connection refused"
 	tcpBrokenPipeErrorCodeMsg   = "%s: broken pipe"
 	netUnknownErrnoErrorCodeMsg = "%s: unknown errno `%d` on %s with message `%s`"

lib/netext/httpext/request_test.go

@@ -230,7 +230,8 @@ func TestURL(t *testing.T) {
 	})
 }
 
-func TestMakeRequestTimeout(t *testing.T) {
+func TestMakeRequestTimeoutInTheMiddle(t *testing.T) {
+	t.Parallel()
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Add("Content-Length", "100000")
 		w.WriteHeader(200)

lib/netext/httpext/transport.go

@@ -246,8 +246,14 @@ func (t *transport) RoundTrip(req *http.Request) (*http.Response, error) {
 
 	var netError net.Error
 	if errors.As(err, &netError) && netError.Timeout() {
-		err = NewK6Error(requestTimeoutErrorCode, requestTimeoutErrorCodeMsg, netError)
+		var netOpError *net.OpError
+		if errors.As(err, &netOpError) && netOpError.Op == "dial" {
+			err = NewK6Error(tcpDialTimeoutErrorCode, tcpDialTimeoutErrorCodeMsg, netError)
+		} else {
+			err = NewK6Error(requestTimeoutErrorCode, requestTimeoutErrorCodeMsg, netError)
+		}
 	}
+
 	t.saveCurrentRequest(&unfinishedRequest{
 		ctx:      ctx,
 		tracer:   tracer,