filesystem: refactor: use errors.Is instead of os.IsNotExist

[efectn]

Description

Suggested way by https://pkg.go.dev/os#IsNotExist
Explain the details for making this change. What existing problem does the pull request solve?

Fixes # (issue)

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• For new functionalities I follow the inspiration of the express js framework and built them similar in usage
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation - /docs/ directory for https://docs.gofiber.io/
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• If new dependencies exist, I have checked that they are really necessary and agreed with the maintainers/community (we want to have as few dependencies as possible)
• I tried to make my code as fast as possible with as few allocations as possible
• For new code I have written benchmarks so that they can be analyzed and improved

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[gaby]

So gopsutil, is only used by the monitor middleware. Thoughts on moving that to contrib and having it use upstream gopsutil?

[efectn]

So gopsutil, is only used by the monitor middleware. Thoughts on moving that to contrib and having it use upstream gopsutil?

I agree about that idea. It's bad idea to include latest gopsutil to go.mod because of it's heavy https://github.com/shirou/gopsutil/blob/master/go.mod. Also it's bad idea to vendor it due to it's unmaintainable and it's really old release, it might have some security issues.

On the other hand; it's breaking change, we should think a bit more on it. What do you think @ReneWerner87