HTTP benchmark tool in golang

main.go

package main

import (
	"fmt"
	"net/http"
	"os"
	"strconv"
	"time"
)

func main() {
	args := os.Args

	if len(args) < 4 {
		panic("usage: bench <url> <requests> <concurrency>")
	}

	url := os.Args[1]

	requests, err := strconv.Atoi(os.Args[2])
	if err != nil {
		panic("invalid number of requests")
	}

	concurrency, err := strconv.Atoi(os.Args[3])
	if err != nil {
		panic("invalid number of concurrent users")
	}

	failed, averageResponseTime := bench(url, requests, concurrency)

	total := requests * concurrency

	fmt.Println("Completed", total-failed, "of", total, "requests")
	fmt.Println("Average response time", averageResponseTime)

}

func bench(url string, requests int, concurrency int) (failed int, average time.Duration) {

	chanFailed := make(chan int)
	chanAverage := make(chan time.Duration)

	for c := 1; c <= concurrency; c++ {
		go func(c int) {
			for r := 1; r <= requests; r++ {
				start := time.Now()

				status := doRequest(url, c)
				if status == 200 {
					chanFailed <- 0
				} else {
					chanFailed <- 1
				}
				elapsed := time.Now().Sub(start)
				chanAverage <- elapsed
			}
		}(c)
	}

	for c := 1; c <= concurrency; c++ {
		for r := 1; r <= requests; r++ {
			f := <-chanFailed
			if f == 1 {
				failed++
			}
			average += <-chanAverage
		}
	}
	average = average / time.Duration(requests*concurrency)

	return failed, average
}

func doRequest(url string, concurrency int) int {
	client := http.Client{
		Timeout: time.Second * 2,
	}

	req, _ := http.NewRequest(http.MethodGet, url, nil)
	req.Header.Set("User-Agent", "perf-test-"+strconv.Itoa(concurrency))

	res, _ := client.Do(req)
	if res == nil {
		return 500
	}

	return res.StatusCode
}