【现象】

2022-01-17 18:32:26,958 ERROR 18500 [-/::1/-/1ms GET /findOne/1] nodejs.ReferenceError: ctx is not defined
    at HomeController.findOne (..\showcase\app\controller\home.js:18:22)
    at Object.callFn (..\showcase\node_modules\egg-core\lib\utils\index.js:44:21)
    at Object.classControllerMiddleware (..\showcase\node_modules\egg-core\lib\loader\mixin\controller.js:87:20)
at Object.callFn (..\showcase\node_modules\@eggjs\router\lib\utils.js:12:21)

解决方法：

const user = await ctx.service.user.find({id:id});

修改为：

const user = await this.ctx.service.user.find({id:id});