From 2733c61d0008d50a877b6bc6ce7cf181d5ae4402 Mon Sep 17 00:00:00 2001
From: TJ Holowaychuk <tj@vision-media.ca>
Date: Mon, 2 Sep 2013 19:31:11 -0700
Subject: [PATCH] docs

---
 docs/guide.md  | 22 ++++++++++++++++++++++
 examples/co.js |  2 +-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/docs/guide.md b/docs/guide.md
index 38a0210..ec07fe6 100644
--- a/docs/guide.md
+++ b/docs/guide.md
@@ -133,5 +133,27 @@ function logger(format){
 }
 ```
 
+## Async operations
+
+  The [Co](https://github.com/visionmedia/co) forms Koa's foundation for generator delegation, allowing
+  you to write non-blocking sequential code. For example this middleware reads the filenames from `./docs`,
+  and then reads the contents of each markdown file in parallel before assigning the body to the joint result.
 
 
+```js
+var fs = require('co-fs');
+
+app.use(function(){
+  return function *(){
+    var paths = yield fs.readdir('docs');
+
+    var files = yield paths.map(function(path){
+      return fs.readFile('docs/' + path, 'utf8');
+    });
+
+    this.type = 'markdown';
+    this.body = files.join('');
+  }
+});
+```
+
diff --git a/examples/co.js b/examples/co.js
index 3ba50f4..f8a995c 100644
--- a/examples/co.js
+++ b/examples/co.js
@@ -15,7 +15,7 @@ app.use(function(){
     });
 
     this.type = 'markdown';
-    this.body = files.join(', ');
+    this.body = files.join('');
   }
 });