My development ubuntu machine does not have the pfring (https://www.ntop.org/guides/pf_ring/index.html ) installed. Without this, VSCode's gopls is unusable.
I'm not using pfring myself, so in my local branch I removed references to pfring and now gopls is happy.
Perhaps adding a separate go.mod in the pfring/ and examples/pfdump/ directory might also fix the problem?
I assume the problem is with the gopls backend, and not VSCode specific.