fix(compute/metadata): fix retry logic to not panic on error

compute/metadata/metadata.go

@@ -312,16 +312,17 @@ func (c *Client) getETag(suffix string) (value, etag string, err error) {
 	for {
 		var err error
 		res, err = c.hc.Do(req)
-		if err == nil {
-			break
+		var code int
+		if res != nil {
+			code = res.StatusCode
 		}
-		if delay, shouldRetry := retryer.Retry(res.StatusCode, err); shouldRetry {
+		if delay, shouldRetry := retryer.Retry(code, err); shouldRetry {
 			if err := gax.Sleep(ctx, delay); err != nil {
 				return "", "", err
 			}
 			continue
 		}
-		return "", "", err
+		break
 	}
 	defer res.Body.Close()
 	if res.StatusCode == http.StatusNotFound {

compute/metadata/retry.go

@@ -43,6 +43,9 @@ type metadataRetryer struct {
 }
 
 func (r *metadataRetryer) Retry(status int, err error) (time.Duration, bool) {
+	if status == 200 {
+		return 0, false
+	}
 	retryOk := shouldRetry(status, err)
 	if !retryOk {
 		return 0, false

compute/metadata/retry_test.go

@@ -87,6 +87,13 @@ func TestMetadataRetryer(t *testing.T) {
 			wantDelay:       0,
 			wantShouldRetry: false,
 		},
+		{
+			name:            "don't retry 200",
+			code:            200,
+			err:             nil,
+			wantDelay:       0,
+			wantShouldRetry: false,
+		},
 	}
 
 	for _, tc := range tests {