title: Async waterfall with mongo db
body: <p>Probably just a basic concept of async. I'd like to check on how we can pass the array variable from mongo result(docs) to the second function. In below code the second console.log doesn't give any output.    </p>
  
  <pre><code>// Retrieve
  var db = require('monk')('localhost/db');
  var async = require('async');
  
  console.log('start');
  
  async.waterfall([
  
      function(callback) {
          var test = db.get('test');
          test.find({}, function(err, docs) {
              console.log(docs);  //OUTPUT OK
              callback(docs);  
  
          });
  
      },
      function(docs, callback) {
          console.log(docs);  //NO OUTPUT
      }
  ])
  </code></pre>