koa-error.js

const Koa = require('koa');
const app = new Koa();

app.use(async (ctx, next) => {
    try {
        await next();
    }catch(error){
        console.error(error);
        ctx.body = "ServerError";
    }
});

app.on('error', (err, ctx) => {
    console.log("因為有中間件統一處理了Error，這裡理論上不會觸發")
});

// response
app.use(ctx => {
    throw new Error("Error");
});

app.listen(3000);