code: func Columns(v interface{}, excluded ...string) ([]string, error) {
  	return columns(v, false, excluded...)
  }
docs: // Columns scans a struct and returns a list of strings
  // that represent the assumed column names based on the
  // db struct tag, or the field name. Any field or struct
  // tag that matches a string within the excluded list
  // will be excluded from the result