code: func GetDefaultCollation(charset string) (string, error) {
  	charset = strings.ToLower(charset)
  	if charset == CharsetBin {
  		return CollationBin, nil
  	}
  	c, ok := charsets[charset]
  	if !ok {
  		return "", errors.Errorf("Unknown charset %s", charset)
  	}
  	return c.DefaultCollation.Name, nil
  }
docs: // GetDefaultCollation returns the default collation for charset.