title: 'admin' $db always loads when I connect to MongoDB 3.6 using mongoose
body: <p>I am upgrading my node project to MongoDB 3.6 using mongoose. (I just NPM installed the latest versions of mongodb and mongoose, mongodb: 3.0.1, and mongoose: 5.0.1).</p>
  
  <p>Regardless of the database name I pass in with my connection string, whenever I run a query that used to work for my project 
  e.g. </p>
  
  <pre><code>configModel.find({type: 'settings'}, function (err, data) {...})
  </code></pre>
  
  <p>I now get an authorization error "MongoError: not authorized on admin to execute command... $db: 'admin'"</p>
  
  <p>This is the connection function I am currently using. I have also tried using mongoose.createConnection with the same result.</p>
  
  <pre><code>var options = {
    autoReconnect: true,
    reconnectTries: Number.MAX_VALUE,
    poolSize: 10
  };
  
  mongoose.connect(connectionString, options, function(err, db){
    ...
  });
  </code></pre>
  
  <p>connectionString is in the format:</p>
  
  <pre><code>mongodb+srv://&lt;USER&gt;:&lt;PASSWORD&gt;@[atlas.mongo].mongodb.net/&lt;DATABASE_NAME&gt; 
  </code></pre>
  
  <p>This also gives me the same result</p>
  
  <pre><code>mongodb+srv://&lt;USER&gt;:&lt;PASSWORD&gt;@[atlas.mongo].mongodb.net/&lt;DATABASE_NAME&gt;?authSource=admin
  </code></pre>
  
  <p>I am able to connect and query my database using Studio 3T with either of the connection strings above, so I think something is going wrong in mongoose.</p>
  
  <p>Any ideas?</p>