Go Middleware

main.go

// Copyright 2016 Vincent Letourneau.

package main

import (
    "fmt"
    "net/http"
)

func AuthMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        fmt.Println("Auth Middleware")
        next.ServeHTTP(w, r)
    })
}

func TestMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        fmt.Println("Test Middleware")
        next.ServeHTTP(w, r)
    })
}

func SayHelloMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        fmt.Println("Hello Middleware")
        next.ServeHTTP(w, r)
    })
}

func LastHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Println("Last Handler")
}

func main() {
    fmt.Println("Server is running...")

    handler := Use(AuthMiddleware, TestMiddleware, SayHelloMiddleware).HandlerFunc(LastHandler)

    http.Handle("/", handler)
    http.ListenAndServe(":3000", nil)
}

middleware.go

// Copyright 2016 Vincent Letourneau.

package main

import "net/http"

type Middleware func(http.Handler) http.Handler

func Use(mw ...Middleware) Middleware {
    return Middleware(func(next http.Handler) http.Handler {
        if next == nil {
            next = http.NewServeMux()
        }
        for i := len(mw) - 1; i >= 0; i-- {
            next = mw[i](next)
        }
        return next
    })
}

func (mw Middleware) Use(middleware ...Middleware) Middleware {
    return Middleware(func(next http.Handler) http.Handler {
        return Use(middleware...).Handler(mw(next))
    })
}

func (mw Middleware) Handler(next http.Handler) http.Handler {
    return mw(next)
}

func (mw Middleware) HandlerFunc(next http.HandlerFunc) http.Handler {
    return mw.Handler(next)
}