JSONFormatter generating malformed JSON while running parallel test case

[ghost]

In my project we are using parallel test(parallel_tests-0.16.0), cucumber(cucumber-1.3.8) and Gherkin(gherkin-2.12.1-java) gesm to generate the HTML reports. In the project we are using JSONFormatter to write a json, due to multithreaded environment it is giving us malformed JSON every time. Please refer the attachment for the same.

If you have any solution to overcome this JSON issue then please suggest us,
Tons of thanks in advance.

[aslakhellesoy]

Dupe of #230