internal/lsp/cache: disable GOPACKAGESDRIVER

In practice, we only support the go command, and now that we rely on the
private packagesinternal APIs to set -mod and -modfile, GOPACKAGESDRIVER
is actively broken. Forcibly disable it.

Change-Id: I91f8c0d29fada2fe87ad9fdfec6ba8c5504c80cd
Reviewed-on: https://go-review.googlesource.com/c/tools/+/268977
Trust: Heschi Kreinick <[email protected]>
Run-TryBot: Heschi Kreinick <[email protected]>
Reviewed-by: Rebecca Stambler <[email protected]>
gopls-CI: kokoro <[email protected]>

Author: heschi

internal/lsp/cache/snapshot.go

@@ -190,10 +190,14 @@ func (s *snapshot) config(ctx context.Context, inv *gocommand.Invocation) *packa
 	verboseOutput := s.view.options.VerboseOutput
 	s.view.optionsMu.Unlock()
 
+	// Forcibly disable GOPACKAGESDRIVER. It's incompatible with the
+	// packagesinternal APIs we use, and we really only support the go commmand
+	// anyway.
+	env := append(append([]string{}, inv.Env...), "GOPACKAGESDRIVER=off")
 	cfg := &packages.Config{
 		Context:    ctx,
 		Dir:        inv.WorkingDir,
-		Env:        inv.Env,
+		Env:        env,
 		BuildFlags: inv.BuildFlags,
 		Mode: packages.NeedName |
 			packages.NeedFiles |