How to set a key in Redis and get the value (I'm building a url shortener)

I’m kind of new to Redis and I’m currently experiencing a project stand-still because I don’t know any other way to set and get in Redis.

My problem is I’m building a url shortener and when the user posts (a POST request) a url to the server, I’m setting the url as the key and a nanoid generated code as the value and sending back the nanoid code to the user. But when the user sends a GET request with the url code to the server I have to check if the url is already cached and redirect the user to the url but I can’t because the actual url as been set as the key not the url code so it will always return undefined. Please can you help me with this problem? Is there some other to do this? Many thanks in advance! Here is the code:

import redis from 'redis';
import http from 'http';
import express from 'express';
import { Router } from 'express';
import { promisify } from 'util';
import { nanoid } from 'nanoid';

interface Handler {
  (req: Request, res: Response, next: NextFunction): Promise<void> | void;
}

interface Route {
  path: string;
  method: string;
  handler: Handler | Handler[];
}

const { PORT = 8080} = process.env;

// I'm using a docker container
const { REDIS_URL = 'redis://cache:6379' } = process.env;

const redisClient = redis.createClient({
  url: REDIS_URL
});

const initCache = async () =>
  new Promise((resolve, reject) => {
    redisClient.on('connect', () => {
      console.log('Redis client connected');
      resolve(redisClient);
    });

    redisClient.on('error', error => reject(error));
  });

async function getShortenedURL(url: string) {
    const urlCode = nanoid(7);
    redisClient.setex(url, 3600, urlCode);
    return urlCode;
}

const getAsync = promisify(redisClient.get).bind(redisClient);

async function getFromCache(key: string) {
  const data = await getAsync(key);
  return data;
}

const routes = [
    {
        path: '/:url',
        method: 'get',
        handler: [
            async ({ params }: Request, res: Response, next: NextFunction) => {
                try {
                    const { url } = params;
                    const result = await getFromCache(url);

                    if (result) {
                       res.redirect(301, result);
                    } else {
                       throw new Error('Invalid url');
                    }
                } catch (error) {
                    console.error(error);
                }
            }
        ]
    },
    {
        path: '/api/url',
        method: 'post',
        handler: [
            async ({ body }: Request, res: Response, next: NextFunction) => {
                const { url } = body;
                const result = await getFromCache(url);
                result ? res.status(200).send(`http://localhost:${PORT}/${result}`) : next();
            },
            async ({ body }: Request, res: Response) => {
                const result = await getShortenedURL(body.url as string);
                res.status(200).send(result);
            }
        ]
    }
];

const applyRoutes = (routes: Route[], router: Router) => {
    for (const route of routes) {
        const { method, path, handler } = route;
        (router as any)[method](path, handler);
    }
};

const router = express();
applyRoutes(routes, router);


const server = http.createServer(router);


async function start() {
    await initCache();
    server.listen(PORT, () => {
        console.log(`Server is running on http://localhost:${PORT}...`)
    }
    );
}

start();