(*net.OpError); ok { t.Logf("operr: %#v", operr) } debugerr(t, err.Err) return default: return } } We need to take a look at the temporary type definition as well as url.Error to see what's going on.
.Error: t.Logf("err: %s, nested err: %#v", err, err.Err) if operr, ok := err.Err.