refactor(io): enhance HTTP flusher handling

internal/utils/io.go

@@ -106,13 +106,38 @@ func (p BidirectionalPipe) Start() error {
 	return errors.Join(srcErr, dstErr)
 }
 
-type httpFlusher interface {
-	Flush() error
+type flushErrorInterface interface {
+	FlushError() error
 }
 
-func getHTTPFlusher(dst io.Writer) httpFlusher {
+type flusherWrapper struct {
+	rw http.Flusher
+}
+
+type rwUnwrapper interface {
+	Unwrap() http.ResponseWriter
+}
+
+func (f *flusherWrapper) FlushError() error {
+	f.rw.Flush()
+	return nil
+}
+
+func getHTTPFlusher(dst io.Writer) flushErrorInterface {
+	// pre-unwrap the flusher to prevent unwrap and check in every loop
 	if rw, ok := dst.(http.ResponseWriter); ok {
-		return http.NewResponseController(rw)
+		for {
+			switch t := rw.(type) {
+			case flushErrorInterface:
+				return t
+			case http.Flusher:
+				return &flusherWrapper{rw: t}
+			case rwUnwrapper:
+				rw = t.Unwrap()
+			default:
+				return nil
+			}
+		}
 	}
 	return nil
 }
@@ -158,7 +183,6 @@ func CopyClose(dst *ContextWriter, src *ContextReader, sizeHint int) (err error)
 		}()
 	}
 	flusher := getHTTPFlusher(dst.Writer)
-	canFlush := flusher != nil
 	for {
 		nr, er := src.Reader.Read(buf)
 		if nr > 0 {
@@ -177,15 +201,10 @@ func CopyClose(dst *ContextWriter, src *ContextReader, sizeHint int) (err error)
 				err = io.ErrShortWrite
 				return
 			}
-			if canFlush {
-				err = flusher.Flush()
+			if flusher != nil {
+				err = flusher.FlushError()
 				if err != nil {
-					if errors.Is(err, http.ErrNotSupported) {
-						canFlush = false
-						err = nil
-					} else {
-						return err
-					}
+					return err
 				}
 			}
 		}