tests: Do not allow forced type asserts (#20905)

internal/http/flush.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2015-2025 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package http
+
+import "net/http"
+
+// Flush the ResponseWriter.
+func Flush(w http.ResponseWriter) {
+	if f, ok := w.(http.Flusher); ok {
+		f.Flush()
+	}
+}