gistfile1.txt

:~$ cat test.go  
package main

import "os"

func main() {
  file, err := os.OpenFile("helloworld", os.O_WRONLY|os.O_CREATE, os.ModePerm)
  if err != nil {
    panic(err)
  }
  defer file.Close()

  err = file.Truncate(1024 * 1024)
  if err != nil {
    panic(err)
  }
}
:~$ go run test.go  
:~$ du -sh helloworld 
0 helloworld