code: func (s *Service) UseDatabase(mongoDbURI string) error {
  	u, err := url.Parse(mongoDbURI)
  	if err != nil {
  		return err
  	}
  	if u.Scheme != "mongodb" {
  		return errors.New("Missing mongodb:// scheme in URI")
  	}
  	s.mongoDbURI = u
  
  	if s.verbose {
  		log.Printf("Connecting to database %s/%s ... ", u.Host, u.Path[1:])
  	}
  	dbSession, err := mgo.Dial(mongoDbURI)
  	if err != nil {
  		return err
  	}
  	if s.verbose {
  		log.Println("Connected")
  	}
  	s.dbSession = dbSession
  	s.col = s.dbSession.DB(s.mongoDbURI.Path[1:]).C("sync")
  	return nil
  }
docs: // UseDatabase connects to a mongoDB database and stores upload JSON
  // responses, along with a source file checksum to prevent uploading
  // the same file twice. Stored information is used by Url() to build
  // a public URL for accessing the uploaded resource.