Dataloaders documentation example does not work without extra steps

[greg-1-anderson]

What happened?

Followed the instructions in the documentation on Dataloaders and received an inscrutable error message:

go run github.com/vektah/dataloaden UserLoader string *github.com/org/project/pkg/graph/model.SiteInfo
unable to gofmt: /path/project/pkg/dataloader/userloader_gen.go:6:1: expected 'IDENT', found 'import'
exit status 2

What's worse, the code generator cleaned up after itself, giving little info about what might have gone wrong (userloader_gen.go does not exist).

What did you expect?

Documentation should contain correct steps to generate a data loader.

Recommended solution

Update the documentation to contain the missing steps described in vektah/dataloaden#35

I created a new file loaders.go containing only a package statement, and then the instructions worked as presented. There are a number of ways this could be addressed; a one-line fix is presented below:

go get github.com/vektah/dataloaden
mkdir dataloader
cd dataloader
echo 'package dataloader' > loaders.go
go run github.com/vektah/dataloaden UserLoader int *gqlgen-tutorials/dataloader/graph/model.User

Then, instruct users to populate the rest of loaders.go with contents similar to the example below after Dataloaden has generated the data loader.

[greg-1-anderson]

Also, tangentially related, to avoid a lint error in the example I replaced:

const loadersKey = "dataloaders"

With:

type key int

const (
       loadersKey key = iota
)

Without this change, the linter reports:

SA1029: should not use built-in type string as key for value; define your own type to avoid collisions (staticcheck)
		ctx := context.WithValue(r.Context(), loadersKey, &Loaders{
		                                      ^