src/welcome: add note about removing go.useLanguageServer setting

Change-Id: I05314faf26b70b4f34099027c5d43edea7ccb4a7
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/286437
Trust: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Suzy Mueller <suzmue@golang.org>
diff --git a/src/welcome.ts b/src/welcome.ts
index d41ac26..5bd08f9 100644
--- a/src/welcome.ts
+++ b/src/welcome.ts
@@ -7,6 +7,7 @@
 // https://github.com/microsoft/vscode-extension-samples/tree/master/webview-sample
 
 import vscode = require('vscode');
+import { getGoConfig } from './config';
 import { extensionId } from './const';
 
 export class WelcomePanel {
@@ -123,6 +124,14 @@
 		// Use a nonce to only allow specific scripts to be run
 		const nonce = getNonce();
 
+		// Add an extra note if the user has already disabled gopls, asking
+		// them to enable it.
+		let alreadyDisabledGopls = '';
+		if (getGoConfig()?.get('useLanguageServer') === false) {
+			alreadyDisabledGopls = `If you previously disabled gopls through the "go.useLanguageServer"
+setting, we recommend removing that setting now.`;
+		}
+
 		return `<!DOCTYPE html>
 			<html lang="en">
 			<head>
@@ -161,7 +170,7 @@
 					Heads up! Gopls, the official Go language server, is now enabled in VS Code by default.
 					Gopls replaces several legacy tools to provide IDE features while editing Go code.
 					See <a href="https://github.com/golang/vscode-go/issues/1037">issue 1037</a> for more
-					information.
+					information. ${alreadyDisabledGopls}
 				</p>
 			</div>