Javascript function not returning variable

Question

I have the following function that is used to call an API.

var unirest = require("unirest");

const fetchUpcomingBySport = async(id) => {
    var req = unirest("GET", "https://bet365-sports-odds.p.rapidapi.com/v1/bet365/upcoming");

    req.query({
        "sport_id": id
    });
    
    req.headers({
        "x-rapidapi-host": "bet365-sports-odds.p.rapidapi.com",
        "x-rapidapi-key": "API-KEY",
        "useQueryString": true
    });
    
    
    req.end(function (res) {
        if (res.error) throw new Error(res.error);
        return(res.body.results);
    });
}

module.exports = fetchUpcomingBySport;

The API call is successful. I can log the 'res.body.results' fine, however the returned value from my call let fixtures = await fetchUpcomingBySport(12)is undefined. I believe that I have to return from outside of the res.end callback like so:

var unirest = require("unirest");

const fetchUpcomingBySport = async(id) => {
    var req = unirest("GET", "https://bet365-sports-odds.p.rapidapi.com/v1/bet365/upcoming");
    let results;
    
    req.query({
        "sport_id": id
    });
    
    req.headers({
        "x-rapidapi-host": "bet365-sports-odds.p.rapidapi.com",
        "x-rapidapi-key": "API KEY",
        "useQueryString": true
    });
    
    
    req.end(function (res) {
        if (res.error) throw new Error(res.error);
        results = res.body.results;
        return;
    });
    
    return results;
}

module.exports = fetchUpcomingBySport;

however when I create a variable 'results' in the beginning of the fetchUpcomingBySport, but when I set the variable = 'res.body.results' it still returns as undefined.

Any ideas?