How to setup dataloaders for GraphQL in graphql-go?

Question

I am using a gqlgen package for Golang and I am trying to implement a Dataloaders. This is the Dataloader I am using: https://github.com/graph-gophers/dataloader

I did everything as in the Tutorial, but I am not able to load all keys as slices of keys. In Node.js if I do something like

loader.load(1)
loader.load(3)
loader.load(3)

In the batch function, for keys, I will receive an array of [1,3]. However, in Golang, I am getting completely different thing.

This is my field resolver

func (r *newsResolver) CreatedBy(ctx context.Context, obj *models.News) (*models.User, error) {
    loader := NewDataLoader()

    thunk := loader.Load(context.TODO(), dataloader.StringKey(obj.CreatedById)) // StringKey is a convenience method that make wraps string to implement `Key` interface
    result, err := thunk()
    if err != nil {
        // handle data error
    }

    log.Printf("value: %#v", result)
    return nil, nil
}

and a Dataloader function

func NewDataLoader() *dataloader.Loader {
    batchFn := func(ctx context.Context, keys dataloader.Keys) []*dataloader.Result {
        var results []*dataloader.Result
        fmt.Println(keys)
        results = append(results, &dataloader.Result{Data: keys})
        return results
    }

    loader := dataloader.NewBatchedLoader(batchFn)
    return loader
}

However, when I print keys, I am getting in a batch function, I am getting each time a slice of a single input. Something like

[2]
[1]
[3]
[1]
[3]

And I think I am supposed to get something like: [2, 1, 3]

Answer 1

You are creating a new dataloader (loader := NewDataLoader()) every time you are using it. This renders it useless.

You should use the same dataloader for the whole request. E.g. storing it in the request context. Some tutorials, I've found:

• https://w11i.me/graphql-server-go-part2-dataloaders
• https://david-yappeter.medium.com/the-importance-of-dataloader-in-graphql-go-4d5214869b20