disable parallel test execution

.travis.yml

@@ -9,6 +9,6 @@ before_script:
 - sudo ntpdate -u time.google.com
 - date
 script:
-- go test -tags json -v v2ray.com/core/...
+- go test -p 1 -tags json -v v2ray.com/core/...
 after_success:
 - ./testing/coverage/coverall

.vscode/tasks.json

@@ -21,7 +21,7 @@
     },
     {
       "taskName": "test",
-      "args": ["v2ray.com/core/..."],
+      "args": ["-p", "1", "v2ray.com/core/..."],
       "isBuildCommand": false
     }
   ]