golang implements multi-coroutine download files (supports breakpoint continuous transmission)

package main

import (
 "fmt"
 "io"
 "os"
 "regexp"
 "strconv"
 "sync"

 "/qianlnk/pgbar"
)

/**
 * need:
 1. Multi-coroutine download file
 2. Breakpoints continue
 **/
func main() {
 //Get the file to be downloaded DownloadFileName := "./"
 //copy file copyFileName := "./"
 storgeFileName := "./"
 //Open the file sfile, err := (DownloadFileName)
 if err != nil {
  panic(err)
 }
 defer ()
 //Get file size info, _ := ()
 downloadSize := ()
 var scount int64 = 1
 if downloadSize%5 == 0 {
  scount *= 5
 } else {
  scount *= 10
 }
 //The size assigned to each coroutine si := downloadSize / scount
 ("Total file size: %v, number of shards: %v, size of each shard: %v\n", downloadSize, scount, si)
 //open copy file
 copyFile, err := (copyFileName, os.O_CREATE|os.O_WRONLY, )
 if err != nil {
  panic(err)
 }
 storgeFile, err := (storgeFileName, os.O_CREATE|os.O_RDWR, )
 if err != nil {
  panic(err)
 }
 defer ()

 var currentIndex int64 = 0
 wg := {}
 ("Coprocess progress bar")
 pgb := ("")
 for ; currentIndex < scount; currentIndex++ {
  (1)
  go func(current int64) {
   p := (((current+1))+"st", int(si))
   // (900, 100)
   b := make([]byte, 1024)
   bs := make([]byte, 16)
   currentIndex, _ := (bs, current*16)
   //Take out all integers   reg := (`\d+`)
   countStr := (string(bs[:currentIndex]))
   total, _ := (countStr, 10, 0)
   progressBar := 1
   for {
    if total >= si {
     ()
     break
    }
    //Read from the specified location    n, err := (b, current*si+total)
    if err ==  {
     ()
     break
    }
    //Start write from the specified location    (b, current*si+total)
    ([]byte((total, 10)+" "), current*16)
    total += int64(n)
    if total >= si/10*int64(progressBar) {
     progressBar += 1
     (int(si / 10))
    }

   }

  }(currentIndex)
 }
 ()
 ()
 (storgeFileName)
 ("Download Completed")
}