add RequestHeader option for websocket conn

relay.go

@@ -7,6 +7,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"log"
+	"net/http"
 	"sync"
 	"time"
 
@@ -36,7 +37,8 @@ func (s Status) String() string {
 }
 
 type Relay struct {
-	URL string
+	URL           string
+	RequestHeader http.Header // e.g. for origin header
 
 	Connection    *Connection
 	subscriptions s.MapOf[string, *Subscription]
@@ -77,7 +79,7 @@ func (r *Relay) Connect(ctx context.Context) error {
 		defer cancel()
 	}
 
-	socket, _, err := websocket.DefaultDialer.DialContext(ctx, r.URL, nil)
+	socket, _, err := websocket.DefaultDialer.DialContext(ctx, r.URL, r.RequestHeader)
 	if err != nil {
 		return fmt.Errorf("error opening websocket to '%s': %w", r.URL, err)
 	}

relay_test.go

@@ -121,9 +121,7 @@ func TestConnectContext(t *testing.T) {
 
 func TestConnectContextCanceled(t *testing.T) {
 	// fake relay server
-	ws := newWebsocketServer(func(conn *websocket.Conn) {
-		io.ReadAll(conn) // discard all input
-	})
+	ws := newWebsocketServer(discardingHandler)
 	defer ws.Close()
 
 	// relay client
@@ -135,6 +133,26 @@ func TestConnectContextCanceled(t *testing.T) {
 	}
 }
 
+func TestConnectWithOrigin(t *testing.T) {
+	// fake relay server
+	// default handler requires origin golang.org/x/net/websocket
+	ws := httptest.NewServer(websocket.Handler(discardingHandler))
+	defer ws.Close()
+
+	// relay client
+	r := &Relay{URL: NormalizeURL(ws.URL), RequestHeader: http.Header{"origin": {"https://example.com"}}}
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	err := r.Connect(ctx)
+	if err != nil {
+		t.Errorf("unexpected error: %v", err)
+	}
+}
+
+func discardingHandler(conn *websocket.Conn) {
+	io.ReadAll(conn) // discard all input
+}
+
 func newWebsocketServer(handler func(*websocket.Conn)) *httptest.Server {
 	return httptest.NewServer(&websocket.Server{
 		Handshake: anyOriginHandshake,