网上很多文件基本都是多协程下载文件要么就只有单协程的断点续传，这里给大家写一个支持有进度条的多协程下载文件，也支持断点续传。
好了，直接看代码就好了，小编已加上详细的解释与说明
```go
package main
import (
"fmt"
"io"
"os"
"regexp"
"strconv"
"sync"
"github.com/qianlnk/pgbar"
)
/**
* 需求:
1. 多协程下载文件
2.断点续连
**/
func main() {
//获取要下载文件
DownloadFileName := "./123.zip"
//copy的文件
copyFileName := "./test.zip"
storgeFileName := "./current.txt"
//打开文件
sfile, err := os.Open(DownloadFileName)
if err != nil {
panic(err)
}
defer sfile.Close()
//获取文件大小
info, _ := sfile.Stat()
downloadSize := info.Size()
var scount int64 = 1
if downloadSize%5 == 0 {
scount *= 5
} else {
scount *= 10
}
//分给每个协程的大小
si := downloadSize / scount
fmt.Printf("文件总大小：%v, 分片数：%v,每个分片大小：%v\n", downloadSize, scount, si)
//open copy file
copyFile, err := os.OpenFile(copyFileName, os.O_CREATE|os.O_WRONLY, os.ModePerm)
if err != nil {
panic(err)
}
storgeFile, err := os.OpenFile(storgeFileName, os.O_CREATE|os.O_RDWR, os.ModePerm)
if err != nil {
panic(err)
}
defer copyFile.Close()
var currentIndex int64 = 0
wg := sync.WaitGroup{}
fmt.Println("协程进度条")
pgb := pgbar.New("")
for ; currentIndex < scount; currentIndex++ {
wg.Add(1)
go func(current int64) {
p := pgb.NewBar(fmt.Sprint((current+1))+"st", int(si))
// p.SetSpeedSection(900, 100)
b := make([]byte, 1024)
bs := make([]byte, 16)
currentIndex, _ := storgeFile.ReadAt(bs, current*16)
//取出所有整数
reg := regexp.MustCompile(`\d+`)
countStr := reg.FindString(string(bs[:currentIndex]))
total, _ := strconv.ParseInt(countStr, 10, 0)
progressBar := 1
for {
if total >= si {
wg.Done()
break
}
//从指定位置开始读
n, err := sfile.ReadAt(b, current*si+total)
if err == io.EOF {
wg.Done()
break
}
//从指定位置开始写
copyFile.WriteAt(b, current*si+total)
storgeFile.WriteAt([]byte(strconv.FormatInt(total, 10)+" "), current*16)
total += int64(n)
if total >= si/10*int64(progressBar) {
progressBar += 1
p.Add(int(si / 10))
}
}
}(currentIndex)
}
wg.Wait()
storgeFile.Close()
os.Remove(storgeFileName)
fmt.Println("下载完成")
}
```
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