Support external store

.eslintrc

@@ -0,0 +1,3 @@
+{
+  "extends": "eslint-config-egg",
+}

.travis.yml

@@ -1,8 +1,8 @@
 sudo: false
 language: node_js
 node_js:
-  - '0.12'
   - '4'
   - '6'
+  - '7'
 script: 'npm run test-travis'
 after_script: 'npm install coveralls@2 && cat ./coverage/lcov.info | coveralls'

Readme.md

@@ -80,12 +80,6 @@ app.use(convert(session(app)));
 // codes
 ```
 
-## Semantics
-
-  This module provides "guest" sessions, meaning any visitor will have a session,
-  authenticated or not. If a session is _new_ a Set-Cookie will be produced regardless
-  of populating the session.
-
 ## API
 
 ### Options
@@ -104,6 +98,21 @@ app.use(convert(session(app)));
   - `valid()`: valid session value before use it
   - `beforeSave()`: hook before save session
 
+### External Session Stores
+
+  Session will store in cookie by default, but it has some disadvantages:
+
+    - Session stored in client side unencrypted.
+    - [Browser cookie always have length limit](http://browsercookielimits.squawky.net/).
+
+  You can store the session content in external stores(redis, mongodb or other DBs) by pass `options.store` with three methods(need to be generator function or async function):
+
+  - `get(key)`: get session object by key
+  - `set(key, sess, maxAge)`: set session object for key, with a `maxAge` (in ms)
+  - `destroy(key)`: destroy session for key
+
+  Once you passed `options.store`, session is strong dependent on your external store, you can't access session if your external store is down. **Use external session stores only if necessary, avoid use session as a cache, keep session lean and stored by cookie!**
+
 ### Session#isNew
 
   Returns __true__ if the session is new.
@@ -132,12 +141,6 @@ if (this.session.isNew) {
 this.session = null;
 ```
 
-## Session Stores
-
-  This module only supports cookie sessions. There are many other modules listed in [koa's wiki](https://github.com/koajs/koa/wiki#wiki-sessions) for sessions that use database storage. Unlike Connect 2.x's session middleware, there is no main "session" middleware that you plugin different stores - each store is a completely different module.
-
-  If you're interested in creating your own koa session store, feel free to fork/extend this repository and add additional tests. At a minimum, it __should__ pass this repositories' tests that apply. Ideally, there would be a central repository with specifications and tests for all koa sessions, which would allow interoperability and consistency between session modules. If you're interested in working on such a project, let us know!
-
 ## License
 
   MIT