Multi-threaded concurrency http client golang version

speed.go

package main

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"net/url"
	"os"
	"runtime"
	"time"
)

var (
	httpClient *http.Client
	content    []string
	fail       []string
)

const (
	//MaxIdleConnections 2
	MaxIdleConnections int = 200
	//RequestTimeout 2
	RequestTimeout int = 30
	//WORKERNUM concurrent  goroutine
	WORKERNUM int = 200
	//CPUNUM max cpu num
	CPUNUM int = 4
	//JOBS all jobs num
	JOBS int = 10 * 10000
	//PROGRESS OLD
	PROGRESS int = 0
)

func createHTTPClient() *http.Client {
	client := &http.Client{
		Transport: &http.Transport{
			MaxIdleConnsPerHost: MaxIdleConnections,
		},
		Timeout: time.Duration(RequestTimeout) * time.Second,
	}

	return client
}

func worker(id int, jobs <-chan int, results chan<- int) {
	for j := range jobs {
		fmt.Println("worker", id, "started  job", j)
		testCPU(j)
		fmt.Println("worker", id, "finished job", j)
		results <- j * 2
	}
}

func init() {
	runtime.GOMAXPROCS(CPUNUM)
	httpClient = createHTTPClient()
	content = readLine("/tmp/hello.txt", PROGRESS)
}

func main() {

	jobs := make(chan int, JOBS)
	results := make(chan int, JOBS)

	for w := 1; w <= WORKERNUM; w++ {
		go worker(w, jobs, results)
	}

	for j := 1; j <= JOBS; j++ {
		jobs <- j
	}
	close(jobs)

	for a := 1; a <= JOBS; a++ {
		<-results
	}
	fmt.Println(fail)
}

func fetch(targetURL string, postData url.Values) (string, error) {
	var request *http.Request

	postDataStr := postData.Encode()
	postDataBytes := []byte(postDataStr)
	postBytesReader := bytes.NewReader(postDataBytes)
	request, _ = http.NewRequest("POST", targetURL, postBytesReader)
	request.Header.Add("Content-Type", "application/x-www-form-urlencoded")

	response, fetchError := httpClient.Do(request)
	if fetchError != nil {
		return "", fetchError
	}
	defer response.Body.Close()
	body, readError := ioutil.ReadAll(response.Body)
	if readError != nil {
		return "", readError
	}
	return string(body), nil
}

func testCPU(lineNumber int) {
	targetURL := "https://example.com/"
	if lineNumber >= len(content) {
		return
	}
	question := url.Values{"apikey": {"something"}, "text": {content[lineNumber-1]}}
	if _, err := fetch(targetURL, question); err != nil {
		fail = append(fail, content[lineNumber-1])
	}
}

func readLine(file string, progress int) []string {
	fi, err := os.Open(file)
	if err != nil {
		fmt.Printf("Error: %s\n", err)
		return nil
	}
	defer fi.Close()

	br := bufio.NewReader(fi)
	var slice []string
	i := 0
	for {
		a, _, c := br.ReadLine()
		i++
		if c == io.EOF {
			break
		}
		fmt.Println(string(a))
		if i <= progress {
			continue
		}
		slice = append(slice, string(a))
	}
	return slice
}