Setup basic prom metrics endpoint (#624)

* Setup basic prom metrics endpoint
* Use default prom handler to expose go runtime metrics

pkg/metrics/server.go

@@ -0,0 +1,19 @@
+package metrics
+
+import (
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/sirupsen/logrus"
+)
+
+func Handler() http.Handler {
+	return promhttp.Handler()
+}
+
+func StartServer(logger *logrus.Logger, path string, addr string) error {
+	logger.WithField("addr", addr).WithField("path", path).Info("starting prometheus metrics server")
+
+	http.Handle(path, Handler())
+	return http.ListenAndServe(addr, nil)
+}