update README

README.md

@@ -1,54 +1,27 @@
 
 # koa-convert
 
-Convert koa generator-based middleware to promise-based middleware.
+Convert koa legacy ( v0.x & v1.x ) generator middleware to promise middleware ( v2.x ).
 
 ## Installation
 
 ```
 $ npm install koa-convert
 ```
 
-## Related Issues
-
-* koa [#415](https://github.com/koajs/koa/issues/415)
-* koa-compose [#27](https://github.com/koajs/compose/pull/27)
-
 ## Usage
 
 ```js
+const Koa = require('koa') // koa v2.x
 const convert = require('koa-convert')
 
-//
-// convert a generator-based middleware to promise-based middleware
-//
-let promiseBased = convert(function* generatorBased(next) {
-    yield next
-    // or
-    // yield* next
-})
-
-//
-// convert array of middleware
-//
-let mws = [
-    // will convert it to promise-based middleware
-    function* generatorMW (next) {
-        yield next
-    },
-    // will convert it to promise-based middleware
-    function* generatorMW(next) {
-        yield* next
-    },
-    // return itself if it's not generator-based middleware
-    function (ctx, next) {
-        return next()
-    },
-    // return itself if it's not generator-based middleware
-    async function (ctx, next) {
-        await next()
-    },
-].map(convert)
+let app = new Koa()
+
+app.use(convert(function* legacyMiddleware(next) {
+  // before
+  yield next
+  // after
+}))
 ```
 
 ## License