📒 docs: thread-safety contracts for mutex-backed public types

[Copilot]

Description

Several public types use internal synchronization but did not state their concurrency guarantees in the API surface. This change adds explicit thread-safety guidance to those type comments so users can distinguish concurrent-safe types from request-scoped/session-scoped objects, while documenting the cases where external synchronization is still required.

• Public API docs
  • Add thread-safety statements to App, Client, CookieJar, Stream, MemoryLock, and both in-memory Storage implementations.
• Qualified concurrency guidance
  • Clarify that Client is safe for concurrent request execution after configuration is complete, that CookieJar.Release must not run concurrently with other methods, and that internal/storage/memory.Storage.Conn() returns a live shared map that still requires external synchronization.
• Session lifecycle clarity
  • Clarify that session.Session and session.Middleware synchronize internal state, but remain request-scoped and must not outlive the request lifecycle.
• App-specific caveat
  • Document App as concurrent-safe while preserving the existing exception for route mutation APIs that explicitly document otherwise.

Example of the updated contract style:

// App denotes the Fiber application.
// App is safe for concurrent use, except for route mutation methods that
// explicitly document otherwise.
type App struct { ... }

Changes introduced

• Benchmarks: No performance changes.
• Documentation Update: Added thread-safety and lifecycle guidance to the affected Go type doc comments in app.go, client/client.go, client/cookiejar.go, middleware/session/session.go, middleware/session/middleware.go, middleware/sse/sse.go, middleware/idempotency/locker.go, internal/memory/memory.go, and internal/storage/memory/memory.go, including qualified caveats where blanket concurrency guarantees would be inaccurate.
• Changelog/What's New: Not applicable.
• Migration Guide: Not applicable.
• API Alignment with Express: Not applicable.
• API Longevity: Clarifies existing concurrency behavior without changing APIs or semantics, and narrows the affected contracts where external synchronization is still required.
• Examples: Inline doc-comment examples only.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• Enhancement (improvement to existing features and functionality)
• Documentation update (changes to documentation)
• Performance improvement (non-breaking change which improves efficiency)
• Code consistency (non-breaking change which improves code reliability and robustness)

Checklist

Before you submit your pull request, please make sure you meet these requirements:

• Followed the inspiration of the Express.js framework for new functionalities, making them similar in usage.
• Conducted a self-review of the code and provided comments for complex or critical parts.
• Updated the documentation in the /docs/ directory for Fiber's documentation.
• Added or updated unit tests to validate the effectiveness of the changes or new features.
• Ensured that new and existing unit tests pass locally with the changes.
• Verified that any new dependencies are essential and have been agreed upon by the maintainers/community.
• Aimed for optimal performance with minimal allocations in the new code.
• Provided benchmarks for the new code to analyze and improve upon.

Commit formatting

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.39%. Comparing base (e5e93e6) to head (bb47e07).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4367   +/-   ##
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  Coverage   91.39%   91.39%           
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  Files         132      132           
  Lines       13098    13098           
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  Hits        11971    11971           
  Misses        710      710           
  Partials      417      417           

Flag	Coverage Δ
unittests	91.39% <ø> (ø)

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[Copilot]

Pull request overview

Adds explicit thread-safety and lifecycle contracts to doc comments for several mutex-backed (or otherwise synchronized) types so users can better understand which APIs are safe to share across goroutines vs. request-scoped objects.

Changes:

• Document concurrency guarantees for core/public types (e.g., App, Client, CookieJar) and selected middleware/internal utilities.
• Clarify session middleware lifecycle expectations (request-scoped; not valid beyond request end).
• Add concurrency statement for SSE Stream and idempotency MemoryLock.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
app.go	Documents App’s intended concurrency contract with route-mutation caveat.
client/client.go	Adds a concurrency statement for Client (needs tighter wording to match implementation).
client/cookiejar.go	Adds a concurrency statement for CookieJar (needs qualification re: Release).
internal/memory/memory.go	States in-memory test/benchmark storage is concurrent-safe.
internal/storage/memory/memory.go	States test storage is concurrent-safe (needs qualification due to Conn() exposing the map).
middleware/idempotency/locker.go	Documents MemoryLock as concurrent-safe.
middleware/session/session.go	Clarifies Session is mutex-protected but request-scoped.
middleware/session/middleware.go	Clarifies Middleware is mutex-protected but request-scoped.
middleware/sse/sse.go	Documents SSE Stream as concurrent-safe.