Problem of returning an array in javascript

Question

I don't understand why my code doesn't work, can someone help me ?

I have a file with all my function (listFunction.mjs) and I want to get an array in testCallApi.mjs, but this didn't work. I got an undefined.

When I do a "console.log(list)", I have a result, but when I want to return this value, that didn't want.

Here is my two files, don't pay attention to the auth, it's for google API.

listFunction.mjs:

export function listGroups(auth) {
    const service = google.admin({version: 'directory_v1', auth});
    var list = [];
    service.groups.list({
        customer: 'my_customer',
        orderBy: 'email',
        maxResults: 10,
        sortOrder: 'ASCENDING',
    }, (err, res) => {
        if (err) return console.error('The API returned an error:', err.message);
        const groups = res.data.groups;
        groups.forEach((group) => {
            list.push(group.email);
        });
        return list;
    });
}

testCallApi.mjs

console.log(listGroups(callAPI()));