fix: fixed data race in result (schemata caching)

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 92.85714% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 92.54%. Comparing base (fb01d6d) to head (e2e4ea9). Report is 7 commits behind head on master.

Files	Patch %	Lines
result.go	92.85%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #182 +/- ## ========================================== - Coverage 93.30% 92.54% -0.77% ========================================== Files 23 23 Lines 3839 3164 -675 ========================================== - Hits 3582 2928 -654 + Misses 203 155 -48 - Partials 54 81 +27 ``` | [Flag](https://app.codecov.io/gh/go-openapi/validate/pull/182/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=go-openapi) | Coverage Δ | | |---|---|---| | [oldstable](https://app.codecov.io/gh/go-openapi/validate/pull/182/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=go-openapi) | `92.54% <92.85%> (-0.77%)` | :arrow_down: | | [stable](https://app.codecov.io/gh/go-openapi/validate/pull/182/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=go-openapi) | `92.54% <92.85%> (-0.77%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=go-openapi#carryforward-flags-in-the-pull-request-comment) to find out more.

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