Merge pull request #2466 from tifayuki/prometheus_go_metrics

add prometheus metrics

configuration/configuration.go

@@ -133,6 +133,11 @@ type Configuration struct {
 		Debug struct {
 			// Addr specifies the bind address for the debug server.
 			Addr string `yaml:"addr,omitempty"`
+			// Prometheus configures the Prometheus telemetry endpoint.
+			Prometheus struct {
+				Enabled bool   `yaml:"enabled,omitempty"`
+				Path    string `yaml:"path,omitempty"`
+			} `yaml:"prometheus,omitempty"`
 		} `yaml:"debug,omitempty"`
 
 		// HTTP2 configuration options