Kong Performace testing framework

### Where is the problem?

https://docs.konghq.com/gateway/latest/plan-and-deploy/performance-testing-framework/

### What happened?

I Tried to execute lua script with kong performace testing framework as given in the above link:
but on execution by following the steps. : got below error

Error → /usr/local/share/lua/5.1/spec/helpers/perf/logger.lua @ 14
suite /usr/local/bin/test_spec.lua
/usr/local/share/lua/5.1/spec/helpers/perf/logger.lua:14: attempt to index global 'ngx' (a nil value)

Though nginx and kong is running.
Please check for the openrusty dependency in testing framework

### What did you expect to happen?

The script should get executed

### Code of Conduct and Community Expectations

- [X] I agree to follow this project's Code of Conduct
- [X] I agree to abide by the Community Expectations

Start with the performance-testing-framework documentation URL and reproduce the reported Lua script execution. Inspect /usr/local/share/lua/5.1/spec/helpers/perf/logger.lua at line 14 and verify the documented dependency and runtime assumptions; done means the documented script executes without the nil global ngx error.

Written by the indexing model from the issue text.