$ npm install koa-flash-message

import Koa from 'koa';
import session from 'koa-generic-session';
import koaRedis from 'koa-redis';
import flashMessage from 'koa-flash-message';
import convert from 'koa-convert';

const redisStore = koaRedis({
  url: config.redisUrl
});

const app = new Koa();

app.keys = [config.secretKeyBase];
app.use(convert(session({
  store: redisStore,
  prefix: '__sess:',
  key: '__sid'
})));

app.use(flashMessage);

ctx.flashMessage.warning = 'Log Out Successfully!';

ctx.state.flashMessage.messages
// or ctx.flashMessage.messages

ctx.state.flashMessage.warning
// or ctx.flashMessage.warning