code: func (v *Validator) Check(password string) error {
  	if strings.TrimSpace(password) == "" {
  		return ErrEmpty
  	}
  	if len(password) < v.options.MinLength {
  		return ErrTooShort
  	}
  	if countUniqueChars(password) < v.options.MinDiff {
  		return ErrTooFewChars
  	}
  
  	// Inspired by cracklib
  	maxrepeat := 3.0 + (0.09 * float64(len(password)))
  	if countSystematicChars(password) > int(maxrepeat) {
  		return ErrTooSystematic
  	}
  
  	return v.foundInDictionaries(password)
  }
docs: // Check validates a password for common flaws
  // It returns nil if the password is considered acceptable.