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:

• Deutsch (de_DE)
• Português Brasileiro (pt_BR)
• 简体中文 (zh_CN)
• 繁體中文 (zh_TW)
• 日本語 (ja_JP)
• Français (fr_FR)
• 한국어 (ko_KR)

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.

Packaging

If you are on Debian, negroni is also available as a
package that
you can install via apt install golang-github-urfave-negroni-dev (at the time
of writing, it is in the sid repositories).

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)

With()

Negroni has a convenience function called With. With takes one or more
Handler instances and returns a new Negroni with the combination of the
receiver's handlers and the new handlers.

// middleware we want to reuse
common := negroni.New()
common.Use(MyMiddleware1)
common.Use(MyMiddleware2)

// `specific` is a new negroni with the handlers from `common` combined with the
// the handlers passed in
specific := common.With(
	SpecificMiddleware1,
	SpecificMiddleware2
)

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")
}

If no address is provided, the PORT environment variable is used instead.
If the PORT environment variable is not defined, the default address will be used.
See Run for a complete description.

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),
))

With() can be used to eliminate redundancy for middlewares shared across
routes.

router := mux.NewRouter()
apiRoutes := mux.NewRouter()
// add api routes here
webRoutes := mux.NewRouter()
// add web routes here

// create common middleware to be shared across routes
common := negroni.New(
	Middleware1,
	Middleware2,
)

// create a new negroni for the api middleware
// using the common middleware as a base
router.PathPrefix("/api").Handler(common.With(
  APIMiddleware1,
  negroni.Wrap(apiRoutes),
))
// create a new negroni for the web middleware
// using the common middleware as a base
router.PathPrefix("/web").Handler(common.With(
  WebMiddleware1,
  negroni.Wrap(webRoutes),
))

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 PanicHandlerFunc 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.PanicHandlerFunc = reportToSentry
  n.Use(recovery)
  n.UseHandler(mux)

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

func reportToSentry(info *negroni.PanicInformation) {
    // write code here to report error to Sentry
}

The middleware simply output the informations on STDOUT by default.
You can customize the output process by using the SetFormatter() function.

You can use also the HTMLPanicFormatter to display a pretty HTML when a crash occurs.

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.Formatter = &negroni.HTMLPanicFormatter{}
  n.Use(recovery)
  n.UseHandler(mux)

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

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] 2017-10-04T14:56:25+02:00