[release] src/utils/pathUtils: return the default go path only if exists

https://go-review.googlesource.com/c/vscode-go/+/276493 meant
to add /usr/local/bin/go to the default path to search, but introduced
a bug - we shouldn't return the path if the go binary doesn't exist.

TODO: This function got complicated over time and deserves proper testing.

For golang/vscode-go#971
Fixes golang/vscode-go#1065

Change-Id: I3ddf90983a1f66d6d76a3f9a50eb528a93904f3c
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/279727
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
(cherry picked from commit dd9c54fa42eeeed478a112d5c26ac4bdaf4d7501)
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/280592
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Suzy Mueller <suzmue@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
diff --git a/src/utils/pathUtils.ts b/src/utils/pathUtils.ts
index 235ca8b..0f693cb 100644
--- a/src/utils/pathUtils.ts
+++ b/src/utils/pathUtils.ts
@@ -104,8 +104,8 @@
 		for (const p of defaultPathsForGo) {
 			if (executableFileExists(p)) {
 				binPathCache[toolName] = p;
+				return {binPath: p, why: 'default'};
-			return {binPath: p, why: 'default'};
 		return {binPath: ''};