Revert "fix file close"

This reverts commit b35b9a2.

Author: wing328

modules/openapi-generator/src/main/resources/go/client.mustache

@@ -592,18 +592,18 @@ func addFile(w *multipart.Writer, fieldName, path string) error {
 	if err != nil {
 		return err
 	}
+	err = file.Close()
 
-	part, err := w.CreateFormFile(fieldName, filepath.Base(path))
 	if err != nil {
 		return err
 	}
 
-	_, err = io.Copy(part, file)
+	part, err := w.CreateFormFile(fieldName, filepath.Base(path))
 	if err != nil {
 		return err
 	}
+	_, err = io.Copy(part, file)
 
-	err = file.Close()
 	return err
 }