Scale python script with Golang

fun.go

package main

import (
  "fmt"
  "time"
  "sync"
  "os/exec"
)
var wg sync.WaitGroup

func preprocessing(n int) {
  defer wg.Done()

  fmt.Printf(">>>>>> %d \n", n)
  out, err := exec.Command("python","app.py").Output()
    if err != nil {
        fmt.Println("error occured")
        fmt.Printf("%s", err)
    }
  
  fmt.Printf(">>>>>> %s \n", out)
  // time.Sleep(time.Second * time.Duration(7))
}

func main() {

  start := time.Now()
	
  for i := 0; i < 100; i++ {
    wg.Add(1)
    go preprocessing(i)
  }
  wg.Wait()

  elapsed := time.Since(start)
  fmt.Printf("Preprocessing  took %s", elapsed)

}