could not import github.com/99designs/gqlgen (cannot find package "github.com/99designs/gqlgen" in GOROOT or GOPATH)

### What happened?
I follow the [Quick Start](https://github.com/99designs/gqlgen?tab=readme-ov-file#quick-start) guide but keep getting this error in VS Code. Things seem to work fine (init, codegen, etc.)

I also get a linter warning that the package is not within a workspace

### What did you expect?
No VS Code errors.

### Minimal graphql.schema and models to reproduce
Not related to graphql.schema. I get the errors after step 1 and step 2 in the [Quick Start](https://github.com/99designs/gqlgen?tab=readme-ov-file#quick-start) guide.

### versions
- `go run github.com/99designs/gqlgen version`?
v0.17.46

- `go version`?
go version go1.22.2 linux/amd64