src/goLanguageServer: send only file URIs to gopls

gopls never handled untitled URIs

Fixes #1559

Change-Id: Ibb52e5ebffa4f82adaa59c1d54ab5a0ba613be37
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/327189
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

Author: hyangah

src/goLanguageServer.ts

@@ -457,22 +457,15 @@ export async function buildLanguageClient(cfg: BuildLanguageClientOption): Promi
 	const goplsWorkspaceConfig = await adjustGoplsWorkspaceConfiguration(cfg, getGoplsConfig(), 'gopls', undefined);
 
 	const documentSelector = [
-		// Filter out unsupported document types, e.g. vsls, git, ssh.
-		// https://docs.microsoft.com/en-us/visualstudio/liveshare/reference/extensions#visual-studio-code-1
-		//
-		// - files
+		// gopls handles only file URIs.
 		{ language: 'go', scheme: 'file' },
 		{ language: 'go.mod', scheme: 'file' },
-		{ language: 'go.sum', scheme: 'file' },
-		// - unsaved files
-		{ language: 'go', scheme: 'untitled' },
-		{ language: 'go.mod', scheme: 'untitled' },
-		{ language: 'go.sum', scheme: 'untitled' }
+		{ language: 'go.sum', scheme: 'file' }
 	];
 
 	// Let gopls know about .tmpl - this is experimental, so enable it only in the experimental mode now.
 	if (isInPreviewMode()) {
-		documentSelector.push({ language: 'tmpl', scheme: 'file' }, { language: 'tmpl', scheme: 'untitled' });
+		documentSelector.push({ language: 'tmpl', scheme: 'file' });
 	}
 	const c = new LanguageClient(
 		'go', // id