lib/controllers/users.js
function get_user_collection(req, res, next) {
		app.db.collection('users', function(error, user_collection) {
			if(error) { throw error; }
			else {
				req.user_collection = user_collection;
				next();
			}
		});
	}
function get_user_collection(req, res, next) {
		app.db.collection('users', function(error, user_collection) {
			if(error) { throw error; }
			else {
				req.user_collection = user_collection;
				next();
			}
		});
	}
function get_user_collection ( req , res , next ) { app . db . collection ( 'users' , function ( error , user_collection ) { if ( error ) { throw error ; } else { req . user_collection = user_collection ; next ( ) ; } } ) ; }
store the user collection into req.user_collection
store the user collection into req . user_collection