Why does it have no effect to enable http compression under koa (always maxAge=0)?

  node.js, question

I use the koa-cache-control plug-in to set the maxAge of cachecontrol. I don’t know why it is completely ineffective to follow the API, and always maxAge=0. Xiaobai asks for advice one by one.
Attach git plug-in linkhttps://github.com/DaMouse404 …

var send = require('koa-send');
 var Koa = require('koa');
 var app = new Koa();
 var Router = require('koa-router');
 var cors = require('koa-cors');
 var koaBody = require('koa-body')();
 var cacheControl = require('koa-cache-control');
 var router = new Router({
 prefix: '/public'
 });
 app.use(gzip());
 app.use(cors())
 .use(router.routes())
 .use(router.allowedMethods());
 app.use(cacheControl({
 maxAge: 500
 }));
 router.get('/:fname/:cname', koaBody, function*() {
 var fname = this.params.fname;
 var cname = this.params.cname;
 Log ("file type" plus fname);
 Log ("file name" plus cname);
 Yield send(this, "./public/ "plus fname plus"/"plus cname);
 })
 var port = 8003;
 app.listen(port);
 Log (boot successful, port: ${port});

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This is the first time to ask a question, please give your advice.

Global variable value transfer