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This example will help you to capture request and response related data then log it.


package middleware

import (


// AccessLog helps log request and response related data.
func AccessLog(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
t := time.Now()

wr := newWriter(w, r, t)

h.ServeHTTP(wr, r)

"http_req_client_ip": wr.reqClientIP,
"http_req_duration": time.Since(t).Milliseconds(),
"http_req_host": wr.reqHost,
"http_req_method": wr.reqMethod,
"http_req_path": wr.reqPath,
"http_req_protocol": wr.reqProto,
"http_req_size": wr.reqSize,
"http_req_time": wr.reqTime,
"http_req_user_agent": wr.reqUserAgent,
"http_res_size": wr.resSize,
"http_res_status": wr.resStatus,

// Acts as an adapter for http.ResponseWriter type to store request and
// response data.
type writer struct {

reqClientIP string
reqHost string
reqMethod string
reqPath string
reqProto string
reqSize int64 // bytes
reqTime string
reqUserAgent string

resStatus int
resSize int // bytes

func newWriter(w http.ResponseWriter, r *http.Request, t time.Time) *writer {
return &writer{
ResponseWriter: w,

reqClientIP: r.Header.Get("X-Forwarded-For"),
reqMethod: r.Method,
reqHost: r.Host,
reqPath: r.RequestURI,
reqProto: r.Proto,
reqSize: r.ContentLength,
reqTime: t.Format(time.RFC3339),
reqUserAgent: r.UserAgent(),

// Overrides http.ResponseWriter type.
func (w *writer) WriteHeader(status int) {
if w.resStatus == 0 {
w.resStatus = status

// Overrides http.ResponseWriter type.
func (w *writer) Write(body []byte) (int, error) {
if w.resStatus == 0 {

var err error
w.resSize, err = w.ResponseWriter.Write(body)

return w.resSize, err

// Overrides http.Flusher type.
func (w *writer) Flush() {
if fl, ok := w.ResponseWriter.(http.Flusher); ok {
if w.resStatus == 0 {


// Overrides http.Hijacker type.
func (w *writer) Hijack() (net.Conn, *bufio.ReadWriter, error) {
hj, ok := w.ResponseWriter.(http.Hijacker)
if !ok {
return nil, nil, fmt.Errorf("the hijacker interface is not supported")

return hj.Hijack()


"http_req_client_ip": "",
"http_req_duration": 33,
"http_req_host": "localhost:8080",
"http_req_method": "POST",
"http_req_path": "/api/v1/leagues",
"http_req_protocol": "HTTP/1.1",
"http_req_size": 133,
"http_req_time": "2021-07-10T22:49:47+01:00",
"http_req_user_agent": "PostmanRuntime/7.26.8",
"http_res_size": 56,
"http_res_status": 201,
"level": "info",
"message": "",
"time": "2021-07-10T22:49:47+01:00"

"http_req_client_ip": "1a01:1c8:411:f815:1:2:961d:22e1",
"http_req_duration": 1000,
"http_req_host": "localhost:8080",
"http_req_method": "GET",
"http_req_path": "/api/v1/leagues/f47a0eaf-cfd3-4842-9a3e-19eda62404a8",
"http_req_protocol": "HTTP/1.1",
"http_req_size": 0,
"http_req_time": "2021-07-10T22:59:50+01:00",
"http_req_user_agent": "Mozilla/5.0 (Android 9; Mobile; rv:88.0) Gecko/88.0 Firefox/88.0",
"http_res_size": 225,
"http_res_status": 200,
"level": "info",
"message": "",
"time": "2021-07-10T22:59:51+01:00"