code: func Diff(left, right []byte) error {
  	lf, err := ioutil.TempFile("/tmp", "actual-file-")
  	if err != nil {
  		return err
  	}
  	defer lf.Close()
  	defer os.Remove(lf.Name())
  
  	rf, err := ioutil.TempFile("/tmp", "expected-file-")
  	if err != nil {
  		return err
  	}
  	defer rf.Close()
  	defer os.Remove(rf.Name())
  
  	_, err = lf.Write(left)
  	if err != nil {
  		return err
  	}
  	lf.Close()
  
  	_, err = rf.Write(right)
  	if err != nil {
  		return err
  	}
  	rf.Close()
  
  	cmd := exec.Command("/usr/bin/diff", "-u", lf.Name(), rf.Name())
  	cmd.Stdout = os.Stdout
  	cmd.Stderr = os.Stderr
  	cmd.Run()
  
  	return nil
  }
docs: // Diff prints the unified diff of the two provided byte slices
  // using the unix diff command.