How to Unregister Handlers in Go's `net/http` Package?

Unregistering Handlers in net/http

In net/http, handlers can be registered and unregistered at runtime. This allows for dynamic configuration of web servers.

Registering Handlers

The following code demonstrates how to register a handler at runtime using a HandlerFactory:

<code class="go">package main

import (
    "fmt"
    "net/http"
)

type MyHandler struct {
    id int
}

func (hf *MyHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintln(w, r.URL.Path)
}

// Creates MyHandler instances and registers them as handlers at runtime
type HandlerFactory struct {
    handler_id int
}

func (hf *HandlerFactory) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    hf.handler_id++
    handler := MyHandler{hf.handler_id}
    handle := fmt.Sprintf("/%d/", hf.handler_id)
    http.Handle(handle, &amp;handler)
}

func main() {
    factory := HandlerFactory{0}
    http.Handle("/create", &amp;factory)
    http.ListenAndServe("localhost:8080", nil)
}</code>

Unregistering Handlers

To unregister a handler, a custom ServerMux can be created and used. This custom ServerMux includes a Deregister method that removes a pattern-to-handler mapping from the map:

<code class="go">// TODO: check if registered and return error if not.
// TODO: possibly remove the automatic permanent link between /dir and /dir/.
func (mux *MyMux) Deregister(pattern string) error {
    mux.mu.Lock()
    defer mux.mu.Unlock()
    del(mux.m, pattern)
    return nil
}</code>

Using this custom ServerMux:

<code class="go">mux := newMux()
mux.Handle("/create", &amp;factory)

srv := &amp;http.Server {
    Addr: localhost:8080
    Handler: mux,
}
srv.ListenAndServe()</code>

Deregistering handlers from this custom ServerMux can be done safely from another goroutine, without affecting the routing of messages by ListenAndServe().

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