Make HTTP middleware easier to use

server/router/example_test.go

Index: server/router/example_test.go
diff --git a/server/router/example_test.go b/server/router/example_test.go
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index 0000000000000000000000000000000000000000..de0fcdc7b8e9b8590a179629eade52e37d837291
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+++ b/server/router/example_test.go
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+// Copyright 2016 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package router_test
+
+import (
+	"fmt"
+	"log"
+	"math/rand"
+	"net/http"
+	"time"
+
+	"golang.org/x/net/context"
+
+	"github.com/luci/luci-go/server/router"
+)
+
+var durations []time.Duration
+
+func Logger(c *router.Context, next router.Handler) {
+	log.Println(c.Request.URL.String())
+	next(c)
+}
+
+func Monitor(c *router.Context, next router.Handler) {
+	start := time.Now()
+	next(c)
+	durations = append(durations, time.Since(start))
+}
+
+func AuthCheck(c *router.Context, next router.Handler) {
+	var authenticated bool
+	if !authenticated {
+		c.WriteHeader(http.StatusUnauthorized)
+		return
+	}
+	next(c)
+}
+
+func GenerateRandom(c *router.Context, next router.Handler) {
+	secret := rand.Int()
+	c.Context = context.WithValue(c.Context, "secret", secret)
+	next(c)
+}
+
+func Root(c *router.Context) {
+	c.WriteHeader(http.StatusOK)
+}
+
+func Hello(c *router.Context) {
+	name := c.Params[0].Value
+	fmt.Fprintf(c, "Hello, %s", name)
+}
+
+func Random(c *router.Context) {
+	s := c.Value("secret").(int)
+	fmt.Fprintf(c, "secret: %d", s)
+}
+
+// Example_createServer demonstrates creating an HTTP server using the imported
+// router package.
+func Example_createServer() {
+	r := router.New()
+	r.Use(router.MiddlewareChain{Logger, Monitor})
+	r.GET("/", nil, Root)
+	r.GET("/hello/:name", nil, Hello)
+
+	auth := r.Subrouter("authenticated")
+	auth.Use(router.MiddlewareChain{AuthCheck})
+	auth.GET("/random", router.MiddlewareChain{GenerateRandom}, Random)
+
+	http.Handle("/", r)
+	log.Fatal(http.ListenAndServe(":8080", nil))

[iannucci, 2016/06/16 00:54:24]

I think you need

  // Output:
  // something
  // something else

For this to actually run as an example test. (go silently ignores it otherwise
:()

[nishanths, 2016/06/16 03:43:27]

Cool, done. :) 
If you have time, please check to make sure it's along the lines of what you
expected.

+}