fix windows build

common/buf/readv_reader_windows.go

@@ -9,6 +9,6 @@ import (
 
 var useReadv = false
 
-func NewReadVReader(reader io.Reader, rawConn syscall.RawConn) *ReadVReader {
+func NewReadVReader(reader io.Reader, rawConn syscall.RawConn) Reader {
 	return nil
 }