src/goTools.ts: disable lint tool if 'staticcheck' is true

This checks both the values of 'ui.diagnostic.staticcheck' as well as
'staticcheck' to properly turn off the linting tools.

Fixes #1867

Change-Id: Ic50b675b40a5d7181e7053c3408e35c8734112e1
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/361794
Trust: Suzy Mueller <suzmue@golang.org>
Run-TryBot: Suzy Mueller <suzmue@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>

Author: suzmue

src/goTools.ts

@@ -208,7 +208,11 @@ export function goplsStaticcheckEnabled(
 	goConfig: { [key: string]: any },
 	goplsConfig: { [key: string]: any }
 ): boolean {
-	if (goConfig['useLanguageServer'] !== true || goplsConfig['ui.diagnostic.staticcheck'] !== true) {
+	if (
+		goConfig['useLanguageServer'] !== true ||
+		goplsConfig['ui.diagnostic.staticcheck'] === false ||
+		(goplsConfig['ui.diagnostic.staticcheck'] === undefined && goplsConfig['staticcheck'] !== true)
+	) {
 		return false;
 	}
 	const features = goConfig['languageServerExperimentalFeatures'];