Optimize `Len` method by counting expired items in expiration queue #140

	name: Go
	on: [push, pull_request]
	jobs:
	test:
	runs-on: ubuntu-latest
	steps:
	- name: Set up Go
	uses: actions/setup-go@v5
	with:
	go-version: ^1.18
	- name: Checkout code
	uses: actions/checkout@v4
	- name: Run tests
	run: go test -race -shuffle on -timeout 1m -coverprofile=covprofile ./...
	- name: Send coverage
	uses: shogo82148/actions-goveralls@v1
	with:
	path-to-profile: covprofile

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