Does not work with empty files

[yuri-karadzhov]

Stream will never be ended if cached content is empty

const cache = require('streaming-cache');
const {Readable} = require('stream');
const cache = new Cache;
...
new Readable({
  read() {
    this.push(''); // Empty content
    this.push(null);
  },
}).pipe(cache.set(key));
ctx.body = cache.get(key);