Deeply nested route groups with inherited middleware chains, group-level overrides, and route-specific middleware composition.

Nested Route Groups with Middleware Inheritance

Build deeply nested route hierarchies where middleware flows from parent to child, with overrides and route-level additions.

Custom middleware

func Logger(prefix string) kern.MiddlewareFunc {
    return func(next http.Handler) http.Handler {
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            log.Printf("[%s] %s %s", prefix, r.Method, r.URL.Path)
            next.ServeHTTP(w, r)
        })
    }
}

func RequireRole(role string) kern.MiddlewareFunc {
    return func(next http.Handler) http.Handler {
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            // role check logic
            next.ServeHTTP(w, r)
        })
    }
}

Three-level group nesting

func main() {
    app := kern.New(kern.WithRecovery())

Level 1: Global middleware

    app.Use(Logger("global"))

Level 2: API group with auth

    api := app.Group("/api/v1", RequireRole("user"))

    api.GET("/profile", func(c *kern.Context) {
        c.Text(200, "user profile")
    })

Level 3: Admin subgroup with stricter middleware

The admin group inherits RequireRole("user") from parent, adds RequireRole("admin"):

    admin := api.Group("/admin", RequireRole("admin"))

    admin.GET("/users", func(c *kern.Context) {
        c.Text(200, "list all users")
    })

    admin.POST("/config", func(c *kern.Context) {
        c.Text(200, "update config")
    })

Level 4: Per-route middleware override

Route-specific middleware runs AFTER group middleware:

    admin.AddConstraints("DELETE", "/users/{id}", kern.Constraints{
        Validate: RequireRole("super-admin"),
    }, func(c *kern.Context) {
        c.Text(200, "delete user")
    })

Independent sub-groups at same level

    public := api.Group("/public")
    public.GET("/health", func(c *kern.Context) {
        c.Text(200, "ok")
    })

    app.Run(":8080")
}

Middleware execution order

Request → global(Logger)
        → api(RequireRole user)
        → admin(RequireRole admin)
        → route(RequireRole super-admin)
        → handler

Key patterns

Inheritance: Child groups inherit all parent middleware
Composition: Multiple middleware stack in declaration order
Route-level: AddConstraints adds middleware for a single route
Override pattern: Add stricter checks deeper in the group hierarchy
Shared prefix: All routes under /api/v1/admin/* share the same middleware chain

Recipe - Nested Route Groups with Middleware Inheritance