[codex] Upgrade Go and polish README

.claudeignore

@@ -0,0 +1,16 @@
+# Local agent/runtime state
+.omx/
+.history/
+
+# VCS and editor metadata
+.git/
+.vscode/
+
+# Generated test and coverage artifacts
+coverage.*
+*.out
+*.test
+
+# Vendored dependencies
+vendor/
+

AGENTS.md

@@ -0,0 +1,34 @@
+# AGENTS.md
+
+## Project
+
+`github.com/maxwu/chainer` is a small Go package for composing `net/http`
+middleware into a final `http.Handler`.
+
+## Working Rules
+
+- Keep changes small, focused, and easy to review.
+- Prefer the existing standard-library-first style; do not add dependencies
+  unless the task explicitly needs one.
+- Preserve the public API unless the user asks for an API change.
+- Update README examples when public usage changes.
+- Do not commit generated coverage artifacts.
+
+## Toolchain
+
+- Go version: 1.26.
+- Local toolchain is managed by `mise.toml`.
+- In sandboxed environments, set `GOCACHE` to a writable temp directory if Go
+  tries to use a restricted cache path.
+
+## Verification
+
+Run the project test target before claiming completion:
+
+```sh
+GOCACHE=/private/tmp/chainer-go-build mise exec -- make test
+```
+
+The target runs formatting, vet, and the CI-aligned test command with race
+detection and atomic coverage.
+

CLAUDE.md

@@ -0,0 +1,4 @@
+# CLAUDE.md
+
+Follow the repository instructions in [AGENTS.md](./AGENTS.md).
+

Makefile

@@ -1,4 +1,3 @@
-
 .PHONY: fmt
 fmt:
 	go fmt ./...
@@ -9,7 +8,7 @@ vet:
 
 .PHONY: test
 test: fmt vet
-	go test -coverprofile=coverage.out github.com/maxwu/chainer/... -v -ginkgo.v -ginkgo.progress -test.v
+	go test -v -count=1 -race -coverprofile=coverage.out -covermode=atomic ./... -labels env=ci
 
 .PHONY: coverage
 coverage:

README.md

@@ -3,28 +3,81 @@
 [![codecov](https://codecov.io/gh/maxwu/chainer/graph/badge.svg?token=JG5TC3BJIR)](https://codecov.io/gh/maxwu/chainer)
 [![Go Report Card](https://goreportcard.com/badge/github.com/maxwu/chainer)](https://goreportcard.com/report/github.com/maxwu/chainer)
 
-Assemble HTTP middleware functions to a http.Handler which processes the request in chained middleware order.
+Chainer is a tiny Go package for assembling `net/http` middleware into a single
+`http.Handler`. Links run in the order they are passed to `NewChain`, and each
+link decides whether to continue to the next handler.
+
+## Requirements
+
+- Go 1.26
+- Optional: [mise](https://mise.jdx.dev/) for local toolchain management
 
 ## Usage
 
+Install the package:
+
+```sh
+go get github.com/maxwu/chainer
+```
+
+Create middleware links and assemble them into a handler:
+
 ```go
 package main
+
 import (
+	"log"
 	"net/http"
+
 	"github.com/maxwu/chainer"
 )
 
+func logger(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		log.Printf("%s %s", r.Method, r.URL.Path)
+		next.ServeHTTP(w, r)
+	})
+}
+
+func requireAuth(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Header.Get("Authorization") == "" {
+			http.Error(w, "missing authorization", http.StatusUnauthorized)
+			return
+		}
+		next.ServeHTTP(w, r)
+	})
+}
+
+func hello(w http.ResponseWriter, _ *http.Request) {
+	w.WriteHeader(http.StatusOK)
+	_, _ = w.Write([]byte("hello"))
+}
+
 func main() {
-	http.Handle("/", chainer.Chain(
-		chainer.MiddlewareFunc(logger),
-		chainer.MiddlewareFunc(authenticator),
-		chainer.MiddlewareFunc(authorizer),
-		chainer.MiddlewareFunc(handler),
-	))
-	http.ListenAndServe(":8080", nil)
+	handler := chainer.NewChain(
+		chainer.LinkFunc(logger),
+		chainer.LinkFunc(requireAuth),
+		chainer.LinkFunc(func(_ http.Handler) http.Handler {
+			return http.HandlerFunc(hello)
+		}),
+	).GetHandler()
+
+	http.Handle("/", handler)
+	log.Fatal(http.ListenAndServe(":8080", nil))
 }
 ```
 
+## Development
+
+Use `mise install` to install the configured Go toolchain, then run:
+
+```sh
+make test
+```
+
 ## References
 
-This project also demonstrates how to use [gotest-labels](github.com/maxwu/gotest-labels) package to select tests by the tags in test case comment block.
+The test suite demonstrates
+[gotest-labels](https://github.com/maxwu/gotest-labels) for selecting tests by
+labels in test comment blocks.

go.mod

@@ -1,6 +1,6 @@
 module github.com/maxwu/chainer
 
-go 1.24
+go 1.26
 
 require (
 	github.com/maxwu/gotest-labels v1.1.1

mise.toml

@@ -0,0 +1,2 @@
+[tools]
+go = "1.26"