text: const Koa = require("koa");
  const Router = require("koa-router");
  const serve = require("koa-static");
  const path = require("path");
  const Pug = require("koa-pug");
  //require internal files
  const instructors = require("./models/instructor");
  const instructor_ids = require("./models/instructor_id");
  const course_ids = require("./models/course_id");
  const course_prices = require("./models/course_price");
  const checkValues = require("./controllers/checkValues");
  //any new
  const app = new Koa();
  const router = new Router();
  const pug = new Pug({
  	viewPath: "views",
  	debug: false,
  	pretty: false,
  	compileDebug: false,
  	basedir: "views",
  	app: app // equals to pug.use(app) and app.use(pug.Koa)
  });
  
  router.get("/", ctx => {
  	ctx.render(`index`);
  });
  
  router.get("/instructor/find_all", ctx => {
  	ctx.render(`find_all`, instructors);
  });
  
  router.get("/instructor/find_by_id/:id", (ctx, next) => {
  	const id = ctx.params.id;
  	instructor_ids.query_instructors_id(id);
  	next();
  });
  
  router.get("/course/find_by_id/:id", (ctx, next) => {
  	const id = ctx.params.id;
  	course_ids.query_course_id(id);
  	next();
  });
  
  router.get("/course/find_by_price/:price", (ctx, next) => {
  	const price = ctx.params.price;
  	course_prices.query_course_price(price);
  	next();
  });
  
  app.use(router.routes());
  app.use(router.allowedMethods());
  app.use(ctx => checkValues.check(ctx));
  
  app.listen(3000);
  