Make sure all the existing test cases are working as expected

### How to reproduce?
Run `go test ./...` at the root in `feat/es7` branch

You can easily see that a lot of test cases get failed, we need to fix it and make sure that all the test cases work as expected.

### Additional Context
We recently upgraded the elastic search version from 6.x to 7.x which has some breaking changes, probably that might be the reason for some failed test cases.