test add headers round tripper

Signed-off-by: manask322 <manask322@gmail.com>

api/prometheus/v1/example_test.go

@@ -199,6 +199,45 @@ func ExampleAPI_queryRangeWithAuthBearerToken() {
 	fmt.Printf("Result:\n%v\n", result)
 }
 
+func ExampleAPI_queryRangeWithAuthBearerTokenHeadersRoundTripper() {
+	client, err := api.NewClient(api.Config{
+		Address: "http://demo.robustperception.io:9090",
+		// We can use amazing github.com/prometheus/common/config helper!
+		RoundTripper: config.NewHeadersRoundTripper(
+			&config.Headers{
+				Headers: map[string]config.Header{
+					"Authorization": {
+						Values: []string{"Bearer secret"},
+					},
+				},
+			},
+			api.DefaultRoundTripper,
+		),
+	})
+	if err != nil {
+		fmt.Printf("Error creating client: %v\n", err)
+		os.Exit(1)
+	}
+
+	v1api := v1.NewAPI(client)
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	r := v1.Range{
+		Start: time.Now().Add(-time.Hour),
+		End:   time.Now(),
+		Step:  time.Minute,
+	}
+	result, warnings, err := v1api.QueryRange(ctx, "rate(prometheus_tsdb_head_samples_appended_total[5m])", r)
+	if err != nil {
+		fmt.Printf("Error querying Prometheus: %v\n", err)
+		os.Exit(1)
+	}
+	if len(warnings) > 0 {
+		fmt.Printf("Warnings: %v\n", warnings)
+	}
+	fmt.Printf("Result:\n%v\n", result)
+}
+
 func ExampleAPI_series() {
 	client, err := api.NewClient(api.Config{
 		Address: "http://demo.robustperception.io:9090",