test server using async toDataURL()

test/server.js

@@ -37,8 +37,13 @@ app.post('/render', function(req, res, next){
     , canvas = new Canvas(width, height)
     , ctx = canvas.getContext('2d')
     , start = new Date;
+
   fn(ctx);
-  res.send({ data: canvas.toDataURL(), duration: new Date - start });
+  var duration = new Date - start;
+
+  canvas.toDataURL(function(err, str){
+    res.send({ data: str, duration: duration });
+  });
 });
 
 app.listen(3000);