“Exported type should have comment or be unexported” golang VS Code

Just add a comment above it, starting with the name of your type (or function, method etc.) like this:

// Agent is ...
type Agent struct {
   name string
   categoryId int
}

This linter error is caused by your Agent type being exported, even if its attributes are not. To not export your type, define it in lowercase like such:

type agent struct {
   name string
   categoryId int
}

The reason why your linter complains about this is that godoc uses those comments to automatically generate documentation for your projects. You can find many examples of such documented Go projects at pkg.go.dev.

If you upload one of your Go projects to GitHub for example, pkg.go.dev will automatically generate a documentation for you using those comments. You can even add runnable code examples and many other things, as shown on go-doc tricks.