package.json: change go.toolsGopath default to null

That is consistent with go.gopath default.

Change-Id: I704197e847d4d89bf26d887e3cf19d82591edcbb
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/283252
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: Suzy Mueller <suzmue@golang.org>
diff --git a/docs/settings.md b/docs/settings.md
index 83cb405..8b36611 100644
--- a/docs/settings.md
+++ b/docs/settings.md
@@ -506,7 +506,7 @@
 
 Location to install the Go tools that the extension depends on if you don't want them in your GOPATH.
 
-Default: ``
+efault: `<nil>`
 
 ### `go.toolsManagement.checkForUpdates`
 
diff --git a/package.json b/package.json
index 4679949..28b3762 100644
--- a/package.json
+++ b/package.json
@@ -1385,8 +1385,11 @@
           "scope": "machine-overridable"
         },
         "go.toolsGopath": {
-          "type": "string",
-          "default": "",
+          "type": [
+            "string",
+            "null"
+          ],
+          "default": null,
           "description": "Location to install the Go tools that the extension depends on if you don't want them in your GOPATH.",
           "scope": "machine-overridable"
         },