Веб на стандартной библиотеке Go — Метрики Prometheus

import (
    "net/http"
    "strconv"

    "github.com/prometheus/client_golang/prometheus"
    "github.com/prometheus/client_golang/prometheus/promauto"
    "github.com/prometheus/client_golang/prometheus/promhttp"
)

type statusRecorder struct {
    http.ResponseWriter
    status int
}

func (r *statusRecorder) WriteHeader(code int) {
    r.status = code
    r.ResponseWriter.WriteHeader(code)
}

var requestsTotal = promauto.NewCounterVec(
    prometheus.CounterOpts{
        Name: "http_requests_total",
        Help: "Total HTTP requests",
    },
    []string{"method", "path", "status"},
)

func metricsMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        rw := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
        next.ServeHTTP(rw, r)
        requestsTotal.WithLabelValues(r.Method, r.URL.Path, strconv.Itoa(rw.status)).Inc()
    })
}

func main() {
    mux := http.NewServeMux()
    mux.Handle("GET /health", metricsMiddleware(http.HandlerFunc(health)))
    mux.Handle("GET /metrics", promhttp.Handler())
    log.Fatal(http.ListenAndServe(":8080", mux))
}