code: func Normalize(email string) string {
  	// Trim whitespaces.
  	email = strings.TrimSpace(email)
  
  	// Trim extra dot in hostname.
  	email = strings.TrimRight(email, ".")
  
  	// Lowercase.
  	email = strings.ToLower(email)
  
  	return email
  }
docs: // Normalize normalizes email address.