您需要添加一个中间件来检查已注册的路由，如果路由未注册，它可以从那里返回。

package main

import (
    "net/http"
)

func routeExistMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Check if the route exists
        if !routeExists(r.URL.Path) {
            http.NotFound(w, r)
            return
        }

        // Call the next handler in the chain
        next.ServeHTTP(w, r)
    })
}

// Dummy function to check if the route exists
func routeExists(path string) bool {
    // Implement your logic here to check if the route exists
    // For simplicity, this example always returns true
    return true
}

func main() {
    // Create a new mux (router)
    mux := http.NewServeMux()

    // Use the routeExistMiddleware for all routes
    mux.Handle("/", routeExistMiddleware(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("Hello, World!"))
    })))

    // Start the server
    http.ListenAndServe(":8080", mux)
}

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此外，我更喜欢使用gofr，它默认情况下会完成所有这些任务。

在"/"下注册你的404处理程序。"/"是可能的最不特定的模式，也匹配每个请求，所以当且仅当没有其他处理程序匹配该请求时才调用它。

package main

import (
        "log"
        "net/http"
)

func main() {
        api := http.NewServeMux()

        api.HandleFunc("/test", func(w http.ResponseWriter, r *http.Request) {
                w.WriteHeader(http.StatusOK)
        })

        // other routes go here

        // catch all
        api.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
                w.WriteHeader(http.StatusNotFound)
                w.Write([]byte("error message goes here"))
        })

        err := http.ListenAndServe(":8080", api)
        log.Fatal(err)
}

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