Promise in golang

Promise.go

var userDetails *user.Details
var userCards []payment.Card
var userPurchases []shop.Purchase

errGroup, groupCtx := errgroup.WithContext(ctx)

errGroup.Go(func() error {
    var err error
    userDetails, err = user.FindDetailsByID(groupCtx, userID)
    return err
})

errGroup.Go(func() error {
    var err error
    userCards, err = payment.FindCardsByUserID(groupCtx, userID)
    return err
})

errGroup.Go(func() error {
    var err error
    userPurchases, err = shop.FindPurchasesByUserID(groupCtx, userID)
    return err
})

err := errGroup.Wait()
if err != nil {
    // ... handle the error
}