Fix mux

Author: Fangliding

common/buf/copy.go

@@ -1,6 +1,7 @@
 package buf
 
 import (
+	"fmt"
 	"io"
 	"sync"
 	"time"
@@ -137,13 +138,20 @@ func CopyOnceTimeout(reader Reader, writer Writer, timeout time.Duration) error
 }
 
 func TryCopyV(reader Reader, writer Writer, options ...CopyOption) error {
+	// too bad section, many type assertions
+	if _, ok := writer.(*BufferToBytesWriter); !ok {
+		return Copy(reader, writer, options...)
+	}
 	var doCopyV bool
 	if tr, ok := reader.(*TimeoutWrapperReader); ok {
+		fmt.Printf("treader internal type: %T\n", reader)
 		if _, ok := tr.Reader.(*SingleReader); ok {
+			fmt.Printf("tsreader internal type: %T\n", tr.Reader)
 			doCopyV = true
 		}
 	}
-	if _, ok := reader.(*SingleReader); ok {
+	if sr, ok := reader.(*SingleReader); ok {
+		fmt.Printf("sreader internal type: %T\n", sr.Reader)
 		doCopyV = true
 	}
 	if !doCopyV {