code: func DiffStringSlices(slice1 []string, slice2 []string) []string {
  	diffStr := []string{}
  	m := map[string]int{}
  
  	for _, s1Val := range slice1 {
  		m[s1Val] = 1
  	}
  	for _, s2Val := range slice2 {
  		m[s2Val] = m[s2Val] + 1
  	}
  
  	for mKey, mVal := range m {
  		if mVal == 1 {
  			diffStr = append(diffStr, mKey)
  		}
  	}
  
  	return diffStr
  }
docs: // DiffStringSlices returns the difference between two string slices.
  // Useful in tests.
  // See:
  // http://stackoverflow.com/questions/19374219/how-to-find-the-difference-between-two-slices-of-strings-in-golang