test: add go1.20 build flag for test case.

ghosind · ghosind · commit 38f210d6e830 · 2024-07-29T01:31:07.000+08:00
Signed-off-by: ghosind &lt;ghosind@gmail.com&gt;
diff --git a/error_go120_test.go b/error_go120_test.go
@@ -1,3 +1,5 @@
+//go:build go1.20
+
 package async
 
 import (
