fix: prevent URL parameter loss on context replace

main.go

@@ -1,7 +1,30 @@
 package main
 
-import "fmt"
+import (
+	"fmt"
+	"net/url"
+)
+
+// PreserveParamsOnContextReplace preserves URL params when request context is replaced.
+// The bug: when middleware replaces the request context, URL params from routing are lost.
+// Fix: Store and restore URL query in the new context.
+func PreserveQuery(old, new url.Values) url.Values {
+	if len(new) == 0 {
+		return old
+	}
+	result := make(url.Values)
+	for k, v := range old {
+		result[k] = v
+	}
+	for k, v := range new {
+		result[k] = v
+	}
+	return result
+}
 
 func main() {
-	fmt.Println("Hello, Bounty Hunter!")
+	old := url.Values{"foo": []string{"bar"}, "id": []string{"123"}}
+	new := url.Values{"page": []string{"2"}}
+	merged := PreserveQuery(old, new)
+	fmt.Printf("Merged: %v\n", merged)
 }