lib/connection-pool.js
function () {
    if (!self.connections.length) {
      self.removeListener('remove', remove);
      self.closing = false;
      return callback();
    }
  }
function () {
    if (!self.connections.length) {
      self.removeListener('remove', remove);
      self.closing = false;
      return callback();
    }
  }
function ( ) { if ( ! self . connections . length ) { self . removeListener ( 'remove' , remove ) ; self . closing = false ; return callback ( ) ; } }
When all of the connections have been removed, call the callback.
When all of the connections have been removed call the callback .