一 ctx.onerror is not a function

TypeError: ctx.onerror is not a function
    at onerror (/Users/xiexingjie/Developer/mcn/demo/server/node_modules/koa/lib/application.js:179:32)
    at AsyncResource.runInAsyncScope (async_hooks.js:197:9)
    at listener (/Users/xiexingjie/Developer/mcn/demo/server/node_modules/on-finished/index.js:170:15)
    at onFinish (/Users/xiexingjie/Developer/mcn/demo/server/node_modules/on-finished/index.js:101:5)
    at callback (/Users/xiexingjie/Developer/mcn/demo/server/node_modules/ee-first/index.js:55:10)
    at ServerResponse.onevent (/Users/xiexingjie/Developer/mcn/demo/server/node_modules/ee-first/index.js:93:5)
    at ServerResponse.emit (events.js:412:35)
    at ServerResponse.emit (domain.js:475:12)
    at onFinish (_http_outgoing.js:792:10)
    at callback (internal/streams/writable.js:513:21)
[ERROR] 10:08:53 TypeError: ctx.onerror is not a function

原因： 使用koa-bodyparser錯誤，koa-bodyparser是個方法

const bodyParser = require("koa-bodyparser");
//錯誤
app.use(bodyParser); 
// 正確
app.use(bodyParser());