add ipinfo middleware

README.md

@@ -49,3 +49,26 @@ import "git.juancwu.dev/juancwu/lightmux-contrib/recoverer"
 
 mux.Use(recoverer.New())
 ```
+
+### `ipinfo`
+
+Looks up the client IP against the [ipinfo.io](https://ipinfo.io) API via the [official Go SDK](https://github.com/ipinfo/go) and attaches the `*ipinfo.Core` result to the request context. Pair with `realip` upstream so the lookup uses the originating client IP rather than the proxy peer.
+
+```go
+import (
+    sdk "github.com/ipinfo/go/v2/ipinfo"
+    "git.juancwu.dev/juancwu/lightmux-contrib/ipinfo"
+    "git.juancwu.dev/juancwu/lightmux-contrib/realip"
+)
+
+client := sdk.NewClient(nil, nil, "YOUR_TOKEN")
+mux.Use(realip.New(), ipinfo.New(client, nil))
+
+mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+    if info, ok := ipinfo.From(r.Context()); ok {
+        fmt.Fprintf(w, "hello from %s, %s\n", info.City, info.Country)
+    }
+})
+```
+
+Loopback, private, link-local, and unspecified addresses are skipped to preserve API quota. Lookup failures are logged at warn level via [splinter](https://git.juancwu.dev/juancwu/splinter) (pass `nil` for `splinter.Default()` resolved at request time, or supply a custom `*splinter.Logger`) and let the request through with no context value — handlers should treat the `From` lookup as optional.