code: func NewMigrationBox(box packd.Walkable, c *Connection) (MigrationBox, error) {
  	fm := MigrationBox{
  		Migrator: NewMigrator(c),
  		Box:      box,
  	}
  
  	err := fm.findMigrations()
  	if err != nil {
  		return fm, errors.WithStack(err)
  	}
  
  	return fm, nil
  }
docs: // NewMigrationBox from a packr.Box and a Connection.