code: func (m *Manager) Save(contract *Contract) (err error) {
  	if contract.ContractId == "" {
  		err = errors.New("Contractid can not be empty")
  		return
  	}
  	if contract.ID == "" {
  		// New Doc!
  		contract.ID = bson.NewObjectId()
  		err = m.collection.Insert(contract)
  		return err
  	}
  	_, err = m.collection.Upsert(bson.M{"contractid": contract.ContractId}, contract)
  	return
  }
docs: //Save contract