code: func CopyFile(dst, src string, mode os.FileMode) {
  	if err := os.MkdirAll(filepath.Dir(dst), 0755); err != nil {
  		log.Fatal(err)
  	}
  	destFile, err := os.OpenFile(dst, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, mode)
  	if err != nil {
  		log.Fatal(err)
  	}
  	defer destFile.Close()
  
  	srcFile, err := os.Open(src)
  	if err != nil {
  		log.Fatal(err)
  	}
  	defer srcFile.Close()
  
  	if _, err := io.Copy(destFile, srcFile); err != nil {
  		log.Fatal(err)
  	}
  }
docs: // CopyFile copies a file.