Golang http atomic vs mutex

atomicTest.go

package main

import (
	"log"
	"net/http"
	"sync/atomic"
)

type redirector struct {
	counter uint32
}

func (r *redirector) handleRedir(w http.ResponseWriter, req *http.Request) {
	w.Write([]byte("OK"))
	atomic.AddUint32(&r.counter, 1)
}

func main() {
	redr := &redirector{counter: 0}
	http.HandleFunc("/test", redr.handleRedir)

	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatal(err)
	}
}
/*
==========================BENCHMARK==========================
URL:                            http://localhost:8080/test

Used Connections:               400
Used Threads:                   8
Total number of calls:          100000

===========================TIMINGS===========================
Total time passed:              21.64s
Avg time per request:           84.16ms
Requests per second:            4620.43
Median time per request:        36.00ms
99th percentile time:           632.00ms
Slowest time for request:       2105.00ms

=============================DATA=============================
Total response body sizes:              199770
Avg response body per request:          2.00 Byte
Transfer rate per second:               9230.24 Byte/s (0.01 MByte/s)
==========================RESPONSES==========================
20X Responses:          99885   (99.89%)
30X Responses:          0       (0.00%)
40X Responses:          0       (0.00%)
50X Responses:          0       (0.00%)
Errors:                 115     (0.11%)
*/

mutexTest.go

package main

import (
	"log"
	"net/http"
	"sync"
)

type redirector struct {
	counter uint32
	sync.Mutex
}

func (r *redirector) handleRedir(w http.ResponseWriter, req *http.Request) {
	w.Write([]byte("OK"))
	r.Lock()
	r.counter++
	r.Unlock()
}

func main() {
	redr := &redirector{counter: 0}
	http.HandleFunc("/test", redr.handleRedir)

	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatal(err)
	}
}

/*
==========================BENCHMARK==========================
URL:                            http://localhost:8080/test

Used Connections:               400
Used Threads:                   8
Total number of calls:          100000

===========================TIMINGS===========================
Total time passed:              22.66s
Avg time per request:           88.44ms
Requests per second:            4412.28
Median time per request:        37.00ms
99th percentile time:           656.00ms
Slowest time for request:       2109.00ms

=============================DATA=============================
Total response body sizes:              199948
Avg response body per request:          2.00 Byte
Transfer rate per second:               8822.27 Byte/s (0.01 MByte/s)
==========================RESPONSES==========================
20X Responses:          99974   (99.97%)
30X Responses:          0       (0.00%)
40X Responses:          0       (0.00%)
50X Responses:          0       (0.00%)
Errors:                 26      (0.03%)
*/