Alice provides a convenient way to chain your HTTP middleware functions and the app handler.

In short, it transforms

Middleware1(Middleware2(Middleware3(App)))

to

alice.New(Middleware1, Middleware2, Middleware3).Then(App)

None of the other middleware chaining solutions behaves exactly like Alice. Alice is as minimal as it gets: in essence, it's just a for loop that does the wrapping for you.

Check out this blog post for explanation how Alice is different from other chaining solutions.

Your middleware constructors should have the form of

func (http.Handler) http.Handler

Some middleware provide this out of the box. For ones that don't, it's trivial to write one yourself.

func myStripPrefix(h http.Handler) http.Handler {
    return http.StripPrefix("/old", h)
}

This complete example shows the full power of Alice.

package main

import (
    "net/http"
    "time"

    "github.com/throttled/throttled"
    "github.com/justinas/alice"
    "github.com/justinas/nosurf"
)

func timeoutHandler(h http.Handler) http.Handler {
    return http.TimeoutHandler(h, 1*time.Second, "timed out")
}

func myApp(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("Hello world!"))
}

func main() {
    th := throttled.Interval(throttled.PerSec(10), 1, &throttled.VaryBy{Path: true}, 50)
    myHandler := http.HandlerFunc(myApp)

    chain := alice.New(th.Throttle, timeoutHandler, nosurf.NewPure).Then(myHandler)
    http.ListenAndServe(":8000", chain)
}

Here, the request will pass throttled first, then an http.TimeoutHandler we've set up, then nosurf and will finally reach our handler.

Note that Alice makes no guarantees for how one or another piece of middleware will behave. Once it passes the execution to the outer layer of middleware, it has no saying in whether middleware will execute the inner handlers. This is intentional behavior.

Alice works with Go 1.0 and higher.

0. Find an issue that bugs you / open a new one.
1. Discuss.
2. Branch off, commit, test.
3. Make a pull request / attach the commits to the issue.