Fix tlsfragment fallback writeAndWaitAck

common/tlsfragment/wait_stub.go

@@ -9,6 +9,10 @@ import (
 )
 
 func writeAndWaitAck(ctx context.Context, conn *net.TCPConn, payload []byte, fallbackDelay time.Duration) error {
+	_, err := conn.Write(payload)
+	if err != nil {
+		return err
+	}
 	time.Sleep(fallbackDelay)
 	return nil
 }