code: func (r *Release) Previous(db *sql.DB) (*Release, error) {
  	tx, err := db.Begin()
  	if err != nil {
  		return nil, err
  	}
  	defer tx.Rollback()
  
  	var prev = &Release{Bundle: r.Bundle}
  	query := fmt.Sprintf(`SELECT version, released_at FROM %s_releases WHERE released_at < ? ORDER BY released_at DESC LIMIT 1`, r.table())
  	row := tx.QueryRow(query, r.ReleasedAt)
  	err = row.Scan(&prev.Version, &prev.ReleasedAt)
  	if err == nil {
  		err = tx.Commit()
  	}
  	return prev, err
  }
docs: // Previous returns the previous release. The Release must fully filled out.