You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: server.go
    path of file: ./repos/frp/pkg/metrics/prometheus
    
    the code of the file until where you have to start completion: package prometheus

import (
	"github.com/prometheus/client_golang/prometheus"

	"github.com/fatedier/frp/server/metrics"
)

const (
	namespace       = "frp"
	serverSubsystem = "server"
)

var ServerMetrics metrics.ServerMetrics = newServerMetrics()

type serverMetrics struct {
	clientCount     prometheus.Gauge
	proxyCount      *prometheus.GaugeVec
	connectionCount *prometheus.GaugeVec
	trafficIn       *prometheus.CounterVec
	trafficOut      *prometheus.CounterVec
}

func (m *serverMetrics) NewClient() {
	m.clientCount.Inc()
}

func (m *serverMetrics) CloseClient() {
	m.clientCount.Dec()
}

func (m *serverMetrics) NewProxy(_ string, proxyType string) {
	m.proxyCount.WithLabelValues(proxyType).Inc()
}

func (m *serverMetrics) CloseProxy(_ string, proxyType string) {
	m.proxyCount.WithLabelValues(proxyType).Dec()
}

func (m *serverMetrics) OpenConnection(name string, proxyType string) {
	m.connectionCount.WithLabelValues(name, proxyType).Inc()
}

func (m *serverMetrics) CloseConnection(name string, proxyType string) {
	m.connectio
    
func newServerMetrics() *serverMetrics {
	m := &serverMetrics{
		clientCount: prometheus.NewGauge(prometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: serverSubsystem,
			Name:      "client_counts",
			Help:      "The current client counts of frps",
		}),
		proxyCount: prometheus.NewGaugeVec(prometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: serverSubsystem,
			Name:      "proxy_counts",
			Help:      "The current proxy counts",
		}, []string{"type"}),
		connectionCount: prometheus.NewGaugeVec(prometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: serverSubsystem,
			Name:      "connection_counts",
			Help:      "The current connection counts",
		}, []string{"name", "type"}),
		trafficIn: prometheus.NewCounterVec(prometheus.CounterOpts{
			Namespace: namespace,
			Subsystem: serverSubsystem,
			Name:      "traffic_in",
			Help:      "The total in traffic",
		}, []string{"name", "type"}),
		trafficOut: prometheus.NewCounterVec(prometheus.CounterOpts{
			Namespace: namespace,
			Subsystem: serverSubsystem,
			Name:      "traffic_out",
			Help:      "The total out traffic",
		}, []string{"name", "type"}),
	}
	prometheus.MustRegister(m.clientCount)
	prometheus.MustRegister(m.proxyCount)
	prometheus.MustRegister(m.connectionCount)
	prometheus.MustRegister(m.trafficIn)
	prometheus.MustRegister(m.trafficOut)
	return m
}