gopls: recognize the go.work file type

For golang/go#50930

Change-Id: I5bae56853f1e913fccd559d2a553ced4200bcb35
Reviewed-on: https://go-review.googlesource.com/c/tools/+/382237
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

internal/lsp/cache/view.go

@@ -247,6 +247,8 @@ func (v *View) FileKind(fh source.FileHandle) source.FileKind {
 		return source.Mod
 	case ".sum":
 		return source.Sum
+	case ".work":
+		return source.Work
 	}
 	exts := v.Options().TemplateExtensions
 	for _, ext := range exts {

internal/lsp/source/util.go

@@ -173,6 +173,8 @@ func FileKindForLang(langID string) FileKind {
 		return Sum
 	case "tmpl", "gotmpl":
 		return Tmpl
+	case "go.work":
+		return Work
 	default:
 		return UnknownKind
 	}
@@ -188,6 +190,8 @@ func (k FileKind) String() string {
 		return "go.sum"
 	case Tmpl:
 		return "tmpl"
+	case Work:
+		return "go.work"
 	default:
 		return fmt.Sprintf("unk%d", k)
 	}

internal/lsp/source/view.go

@@ -534,6 +534,8 @@ const (
 	Sum
 	// Tmpl is a template file.
 	Tmpl
+	// Work is a go.work file.
+	Work
 )
 
 // Analyzer represents a go/analysis analyzer with some boolean properties