Fix SplitHTTP H3 waited for downResponse before uploading

#3560 (comment)

transport/internet/splithttp/client.go

@@ -9,6 +9,7 @@ import (
 	"net/http/httptrace"
 	"sync"
 
+	"github.com/quic-go/quic-go/http3"
 	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/errors"
 	"github.com/xtls/xray-core/common/net"
@@ -94,6 +95,10 @@ func (c *DefaultDialerClient) OpenDownload(ctx context.Context, baseURL string)
 		gotDownResponse.Close()
 	}()
 
+	if _, h3 := c.download.Transport.(*http3.RoundTripper); h3 {
+		gotConn.Close()
+	}
+
 	// we want to block Dial until we know the remote address of the server,
 	// for logging purposes
 	<-gotConn.Wait()