feat. jwt Middleware

+const jwt = require("jsonwebtoken");
+const User = require('../models/user');
+
+const jwtMiddleware = async (ctx, next) => {
+    const token = ctx.cookies.get("access_token");
+    if(!token) {
+        return next();
+    }
+
+    try {
+        const decoded = jwt.verify(token, process.env.JWT_SECRET);
+        ctx.state.user = {
+            _id : decoded._id,
+            userId : decoded.userId
+        };
+        const now = Math.floor(Date.now() / 1000);
+        if (decoded.exp - now < 60 * 60 * 24 * 3.5) {
+            const user = await User.findById(decoded._id);
+            const token = user.generateToken();
+
+            ctx.cookies.set('access_token', token, {
+                httpOnly : true,
+                maxAge : 1000 * 60 * 60 * 24 * 7
+            })
+        }
+
+    } catch(e) {
+        ctx.state.user = null;
+    }
+
+    return next();
+
+};
+
+module.exports = jwtMiddleware;