minio/vendor/github.com/urfave/negroni

Negroni

Notice: This is the library formerly known as github.com/codegangsta/negroni -- Github will automatically redirect requests to this repository, but we recommend updating your references for clarity.

Negroni is an idiomatic approach to web middleware in Go. It is tiny, non-intrusive, and encourages use of net/http Handlers.

If you like the idea of Martini, but you think it contains too much magic, then Negroni is a great fit.

Language Translations:

• German (de_DE)
• Português Brasileiro (pt_BR)
• 简体中文 (zh_cn)
• 繁體中文 (zh_tw)
• 日本語 (ja_JP)

Getting Started

After installing Go and setting up your GOPATH, create your first .go file. We'll call it server.go.

package main

import (
  "fmt"
  "net/http"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    fmt.Fprintf(w, "Welcome to the home page!")
  })

  n := negroni.Classic() // Includes some default middlewares
  n.UseHandler(mux)

  http.ListenAndServe(":3000", n)
}

Then install the Negroni package (NOTE: >= go 1.1 is required):

go get github.com/urfave/negroni

Then run your server:

go run server.go

You will now have a Go net/http webserver running on localhost:3000.

Is Negroni a Framework?

Negroni is not a framework. It is a middleware-focused library that is designed to work directly with net/http.

Routing?

Negroni is BYOR (Bring your own Router). The Go community already has a number of great http routers available, and Negroni tries to play well with all of them by fully supporting net/http. For instance, integrating with Gorilla Mux looks like so:

router := mux.NewRouter()
router.HandleFunc("/", HomeHandler)

n := negroni.New(Middleware1, Middleware2)
// Or use a middleware with the Use() function
n.Use(Middleware3)
// router goes last
n.UseHandler(router)

http.ListenAndServe(":3001", n)

negroni.Classic()

negroni.Classic() provides some default middleware that is useful for most applications:

• negroni.Recovery - Panic Recovery Middleware.
• negroni.Logger - Request/Response Logger Middleware.
• negroni.Static - Static File serving under the "public" directory.

This makes it really easy to get started with some useful features from Negroni.

Handlers

Negroni provides a bidirectional middleware flow. This is done through the negroni.Handler interface:

type Handler interface {
  ServeHTTP(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc)
}

If a middleware hasn't already written to the ResponseWriter, it should call the next http.HandlerFunc in the chain to yield to the next middleware handler. This can be used for great good:

func MyMiddleware(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
  // do some stuff before
  next(rw, r)
  // do some stuff after
}

And you can map it to the handler chain with the Use function:

n := negroni.New()
n.Use(negroni.HandlerFunc(MyMiddleware))

You can also map plain old http.Handlers:

n := negroni.New()

mux := http.NewServeMux()
// map your routes

n.UseHandler(mux)

http.ListenAndServe(":3000", n)

Run()

Negroni has a convenience function called Run. Run takes an addr string identical to http.ListenAndServe.

package main

import (
  "github.com/urfave/negroni"
)

func main() {
  n := negroni.Classic()
  n.Run(":8080")
}

In general, you will want to use net/http methods and pass negroni as a Handler, as this is more flexible, e.g.:

package main

import (
  "fmt"
  "log"
  "net/http"
  "time"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    fmt.Fprintf(w, "Welcome to the home page!")
  })

  n := negroni.Classic() // Includes some default middlewares
  n.UseHandler(mux)

  s := &http.Server{
    Addr:           ":8080",
    Handler:        n,
    ReadTimeout:    10 * time.Second,
    WriteTimeout:   10 * time.Second,
    MaxHeaderBytes: 1 << 20,
  }
  log.Fatal(s.ListenAndServe())
}

Route Specific Middleware

If you have a route group of routes that need specific middleware to be executed, you can simply create a new Negroni instance and use it as your route handler.

router := mux.NewRouter()
adminRoutes := mux.NewRouter()
// add admin routes here

// Create a new negroni for the admin middleware
router.PathPrefix("/admin").Handler(negroni.New(
  Middleware1,
  Middleware2,
  negroni.Wrap(adminRoutes),
))

If you are using Gorilla Mux, here is an example using a subrouter:

router := mux.NewRouter()
subRouter := mux.NewRouter().PathPrefix("/subpath").Subrouter().StrictSlash(true)
subRouter.HandleFunc("/", someSubpathHandler) // "/subpath/"
subRouter.HandleFunc("/:id", someSubpathHandler) // "/subpath/:id"

// "/subpath" is necessary to ensure the subRouter and main router linkup
router.PathPrefix("/subpath").Handler(negroni.New(
  Middleware1,
  Middleware2,
  negroni.Wrap(subRouter),
))

Bundled Middleware

Static

This middleware will serve files on the filesystem. If the files do not exist, it proxies the request to the next middleware. If you want the requests for non-existent files to return a 404 File Not Found to the user you should look at using http.FileServer as a handler.

Example:

package main

import (
  "fmt"
  "net/http"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    fmt.Fprintf(w, "Welcome to the home page!")
  })

  // Example of using a http.FileServer if you want "server-like" rather than "middleware" behavior
  // mux.Handle("/public", http.FileServer(http.Dir("/home/public")))

  n := negroni.New()
  n.Use(negroni.NewStatic(http.Dir("/tmp")))
  n.UseHandler(mux)

  http.ListenAndServe(":3002", n)
}

Will serve files from the /tmp directory first, but proxy calls to the next handler if the request does not match a file on the filesystem.

Recovery

This middleware catches panics and responds with a 500 response code. If any other middleware has written a response code or body, this middleware will fail to properly send a 500 to the client, as the client has already received the HTTP response code. Additionally, an ErrorHandlerFunc can be attached to report 500's to an error reporting service such as Sentry or Airbrake.

Example:

package main

import (
  "net/http"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    panic("oh no")
  })

  n := negroni.New()
  n.Use(negroni.NewRecovery())
  n.UseHandler(mux)

  http.ListenAndServe(":3003", n)
}

Will return a 500 Internal Server Error to each request. It will also log the stack traces as well as print the stack trace to the requester if PrintStack is set to true (the default).

Example with error handler:

package main

import (
  "net/http"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    panic("oh no")
  })

  n := negroni.New()
  recovery := negroni.NewRecovery()
  recovery.ErrorHandlerFunc = reportToSentry
  n.Use(recovery)
  n.UseHandler(mux)

  http.ListenAndServe(":3003", n)
}

func reportToSentry(error interface{}) {
    // write code here to report error to Sentry
}

Logger

This middleware logs each incoming request and response.

Example:

package main

import (
  "fmt"
  "net/http"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    fmt.Fprintf(w, "Welcome to the home page!")
  })

  n := negroni.New()
  n.Use(negroni.NewLogger())
  n.UseHandler(mux)

  http.ListenAndServe(":3004", n)
}

Will print a log similar to:

[negroni] Started GET /
[negroni] Completed 200 OK in 145.446µs

on each request.

Third Party Middleware

Here is a current list of Negroni compatible middlware. Feel free to put up a PR linking your middleware if you have built one:

Middleware	Author	Description
binding	Matt Holt	Data binding from HTTP requests into structs
cloudwatch	Colin Steele	AWS cloudwatch metrics middleware
cors	Olivier Poitrey	Cross Origin Resource Sharing (CORS) support
csp	Awake Networks	Content Security Policy (CSP) support
delay	Jeff Martinez	Add delays/latency to endpoints. Useful when testing effects of high latency
New Relic Go Agent	Yadvendar Champawat	Official New Relic Go Agent (currently in beta)
gorelic	Jingwen Owen Ou	New Relic agent for Go runtime
Graceful	Tyler Bunnell	Graceful HTTP Shutdown
gzip	phyber	GZIP response compression
JWT Middleware	Auth0	Middleware checks for a JWT on the Authorization header on incoming requests and decodes it
logrus	Dan Buch	Logrus-based logger
oauth2	David Bochenski	oAuth2 middleware
onthefly	Alexander Rødseth	Generate TinySVG, HTML and CSS on the fly
permissions2	Alexander Rødseth	Cookies, users and permissions
prometheus	Rene Zbinden	Easily create metrics endpoint for the prometheus instrumentation tool
render	Cory Jacobsen	Render JSON, XML and HTML templates
RestGate	Prasanga Siripala	Secure authentication for REST API endpoints
secure	Cory Jacobsen	Middleware that implements a few quick security wins
sessions	David Bochenski	Session Management
stats	Florent Messa	Store information about your web application (response time, etc.)
VanGoH	Taylor Wrobel	Configurable AWS-Style HMAC authentication middleware
xrequestid	Andrea Franz	Middleware that assigns a random X-Request-Id header to each request
mgo session	Joel James	Middleware that handles creating and closing mgo sessions per request

Examples

Alexander Rødseth created mooseware, a skeleton for writing a Negroni middleware handler.

Live code reload?

gin and fresh both live reload negroni apps.

Essential Reading for Beginners of Go & Negroni

• Using a Context to pass information from middleware to end handler
• Understanding middleware

About

Negroni is obsessively designed by none other than the Code Gangsta