internal/lsp: ignore errors when finding workspace modules

Fixes golang/go#41558

Change-Id: If00cdb310575ac195ce8ebce7f156e0daa192b8d
Reviewed-on: https://go-review.googlesource.com/c/tools/+/256578
Trust: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

internal/lsp/cache/session.go

@@ -256,8 +256,9 @@ func findWorkspaceModules(ctx context.Context, root span.URI, options *source.Op
 	// Walk the view's folder to find all modules in the view.
 	modules := make(map[span.URI]*moduleRoot)
 	return modules, filepath.Walk(root.Filename(), func(path string, info os.FileInfo, err error) error {
+		// Ignore any errors we may encounter while visiting files.
 		if err != nil {
-			return err
+			return filepath.SkipDir
 		}
 		// For any path that is not the workspace folder, check if the path
 		// would be ignored by the go command. Vendor directories also do not