refactor: New() returns (*Limiter, error) instead of hiding errors

[cnlangzi]

Summary by Sourcery

Change limiter construction to return errors from New instead of panicking and update callers accordingly.

Enhancements:

• Make New return (*Limiter, error) so initialization failures are surfaced to callers instead of causing a panic.

Documentation:

• Document the new error-returning New constructor in README examples and simplify Allow usage to a boolean check.

Tests:

• Update tests and benchmarks to use the new New signature and fail explicitly when construction returns an error.

Chores:

• Adjust the example program to handle construction errors from New and ensure the limiter is always closed.

[sourcery-ai]

Reviewer's Guide

Refactors Limiter construction so New returns (*Limiter, error) instead of panicking on knownbots initialization failure, and updates tests, examples, and documentation to handle the new error-aware API and slightly simplify Allow usage in the README.

Sequence diagram for Limiter creation with error-aware New

sequenceDiagram
    actor App
    participant Botrate as Botrate_New
    participant Knownbots as Knownbots_New

    App->>Botrate: New(opts...)
    activate Botrate
    Botrate->>Knownbots: New()

    alt Knownbots initialization succeeds
        Knownbots-->>Botrate: validator, nil error
        Botrate-->>App: limiter, nil error
    else Knownbots initialization fails
        Knownbots-->>Botrate: nil, error
        Botrate-->>App: nil, error
    end
    deactivate Botrate

Loading

Class diagram for updated Limiter construction via New

classDiagram
    class Config

    class Limiter {
        -cfg Config
    }

    class Botrate {
        +New(opts Option) *Limiter, error
    }

    class Knownbots {
        +New() Validator, error
    }

    Botrate ..> Limiter
    Botrate ..> Knownbots
    Limiter ..> Knownbots

Loading

File-Level Changes

Change	Details	Files
Make Limiter constructor error-aware and propagate knownbots initialization failures to callers.	Change New to return (*Limiter, error) instead of *Limiter. Replace panic on knownbots.New failure with returning nil and the error. Return (l, nil) on successful limiter creation. Update all tests and benchmarks to capture the error from New, fail early on non-nil errors, and reuse the err variable where appropriate. Update README and example code to use the new New signature, including error checks around limiter and knownbots construction, and to slightly simplify the example Allow handler to return a generic 429 response.	limiter.go botrate_test.go README.md example/main.go

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[github-actions]

Benchmark Results

[sourcery-ai]

Hey - I've found 1 issue, and left some high level feedback:

• The tests now have a lot of repeated l, err := New(...) / if err != nil { t.Fatalf(...) } boilerplate; consider introducing a small test helper like newLimiterTB(tb testing.TB, opts ...Option) *Limiter to centralize error handling and keep individual tests focused on behavior.
• The README example handler changed from using result.Reason to a generic 429 Too Many Requests for all failures; if this alters the intended public behavior (distinguishing fake bots vs rate limiting), consider either preserving the richer responses or adding a separate example to demonstrate the more detailed handling.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The tests now have a lot of repeated `l, err := New(...)` / `if err != nil { t.Fatalf(...) }` boilerplate; consider introducing a small test helper like `newLimiterTB(tb testing.TB, opts ...Option) *Limiter` to centralize error handling and keep individual tests focused on behavior.
- The README example handler changed from using `result.Reason` to a generic `429 Too Many Requests` for all failures; if this alters the intended public behavior (distinguishing fake bots vs rate limiting), consider either preserving the richer responses or adding a separate example to demonstrate the more detailed handling.

## Individual Comments

### Comment 1
<location> `botrate_test.go:13-15` </location>
<code_context>

 func TestLimiter_New(t *testing.T) {
-	l := New()
+	l, err := New()
+
+	if err != nil {
+		t.Fatalf("New() returned error: %v", err)
+	}
</code_context>

<issue_to_address>
**issue (testing):** Add a test that covers the failure case where New() returns a non-nil error

Current tests only cover the success path of `New()` and verify that it returns no error. To validate the new behavior when `New()` fails (e.g., when `knownbots.New()` returns an error), add a test that forces this failure and asserts `New()` returns `nil, err` instead of panicking. You may need light dependency injection or a test-only hook around the knownbots constructor to simulate the failure.
</issue_to_address>

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