code: func (m *DbMap) Begin() (*Transaction, error) {
  	if m.logger != nil {
  		now := time.Now()
  		defer m.trace(now, "begin;")
  	}
  	tx, err := begin(m)
  	if err != nil {
  		return nil, err
  	}
  	return &Transaction{
  		dbmap:  m,
  		tx:     tx,
  		closed: false,
  	}, nil
  }
docs: // Begin starts a gorp Transaction