## Summary
Hoists the `otter.LoaderFunc` closure in `GetUnCommonHeader` to a
package-level `loader` var, so it is allocated once at init time instead
of being re-created on every call.
This is a minor cleanup — the previous code created a new `LoaderFunc`
closure each time `GetUnCommonHeader` was called. While otter's
cache-hit path is fast enough that this doesn't show a measurable
difference in end-to-end benchmarks, avoiding the repeated allocation is
strictly better.
## What changed
**Before** (closure created per call):
```go
func GetUnCommonHeader(ctx context.Context, key string) string {
phpHeaderKey, err := headerKeyCache.Get(
ctx,
key,
otter.LoaderFunc[string, string](func(_ context.Context, key string) (string, error) {
return "HTTP_" + headerNameReplacer.Replace(strings.ToUpper(key)) + "\x00", nil
}),
)
...
}
```
**After** (closure allocated once):
```go
var loader = otter.LoaderFunc[string, string](func(_ context.Context, key string) (string, error) {
return "HTTP_" + headerNameReplacer.Replace(strings.ToUpper(key)) + "\x00", nil
})
func GetUnCommonHeader(ctx context.Context, key string) string {
phpHeaderKey, err := headerKeyCache.Get(ctx, key, loader)
...
}
```
## Benchmarks
Apple M1 Pro, 8 runs, `benchstat` comparison — no regressions, no extra
allocations:
| Benchmark | main | PR | vs base |
|---|---|---|---|
| HelloWorld | 41.81µ ± 2% | 42.75µ ± 5% | ~ (p=0.065) |
| ServerSuperGlobal | 73.36µ ± 2% | 74.20µ ± 3% | ~ (p=0.105) |
| UncommonHeaders | 69.03µ ± 3% | 68.71µ ± 1% | ~ (p=0.382) |
All results within noise. Zero change in allocations.
This PR:
- moves state.go to its own module
- moves the phpheaders test the phpheaders module
- simplifies backoff.go
- makes the backoff error instead of panic (so it can be tested)
- removes some unused C structs
