[release] src/goInstallTools.ts: return a rejected promise when go isn't found

If Go is not found, return a rejected promise, so, the promise
chaining can work. updateGoVarsFromConfig is not declared as an
async, so returning nothing means returning nothing.

Fixes golang/vscode-go#660

Change-Id: I16f73ca057f3b6bb220a754afc1baa43cc891c22
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/255963
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Suzy Mueller <suzmue@golang.org>
(cherry picked from commit 8e9cae79cd4df94a06d30722c4ce6935f58e4e9b)
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/257603
diff --git a/src/goInstallTools.ts b/src/goInstallTools.ts
index 218b58e..13824e7 100644
--- a/src/goInstallTools.ts
+++ b/src/goInstallTools.ts
@@ -347,7 +347,7 @@
 	const goRuntimePath = getBinPath('go', false);
 	if (!goRuntimePath) {
-		return;
+		return Promise.reject();
 	return new Promise<void>((resolve, reject) => {
@@ -482,7 +482,7 @@
 	const choice = await vscode.window.showErrorMessage(
-		`Failed to find the "go" binary in either GOROOT(${getCurrentGoRoot()}) or PATH(${envPath}. ` +
+		`Failed to find the "go" binary in either GOROOT(${getCurrentGoRoot()}) or PATH(${envPath}). ` +
 		`Check PATH, or Install Go and reload the window.`,
 		'Go to Download Page'