build/all.bash: add go test in ci test

Change-Id: Icc70420f489f67242fb4a85d7c02a64d5cb9b70d
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/401254
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jamal Carvalho <jamal@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
diff --git a/build/all.bash b/build/all.bash
index de29a6a..a0d858a 100755
--- a/build/all.bash
+++ b/build/all.bash
@@ -55,6 +55,11 @@
 
   echo "**** Check if vsce works ****"
   vsce package
+
+  echo "**** Run Go tests ****"
+  go test ./...
+  # TODO(hyangah): see if go clean -modcache makes kokoro builder happy
+  go clean -modcache
 }
 
 run_test_in_docker() {