examples: Add custom labels example

Signed-off-by: Ying WANG <ying.wang@grafana.com>

examples/customlabels/main.go

@@ -0,0 +1,44 @@
+// Copyright 2022 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// A simple example of how to add fixed custom labels to all metrics exported by the origin collector.
+// For more details, see the documentation: https://pkg.go.dev/github.com/prometheus/client_golang/prometheus#WrapRegistererWith
+
+package main
+
+import (
+	"flag"
+	"log"
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/collectors"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+var addr = flag.String("listen-address", ":8080", "The address to listen on for HTTP requests.")
+
+func main() {
+	flag.Parse()
+
+	// Create a new registry.
+	reg := prometheus.NewRegistry()
+	prometheus.WrapRegistererWith(prometheus.Labels{"serviceName": "bartek"}, reg).MustRegister(
+		collectors.NewGoCollector(),
+		collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}),
+	)
+
+	// Expose the registered metrics via HTTP.
+	http.Handle("/metrics", promhttp.HandlerFor(reg, promhttp.HandlerOpts{}))
+	log.Fatal(http.ListenAndServe(*addr, nil))
+}