Make HTTP middleware easier to use

appengine/logdog/coordinator/config/middleware.go

 // Copyright 2015 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 config
 
 import (
         "net/http"
 
-        "github.com/julienschmidt/httprouter"
         log "github.com/luci/luci-go/common/logging"
-        "github.com/luci/luci-go/server/middleware"
-        "golang.org/x/net/context"
+        "github.com/luci/luci-go/server/router"
 )
 
 // WithConfig is a middleware.Handler that installs the LogDog Coordinator
 // configuration into the Context.
-func WithConfig(h middleware.Handler) middleware.Handler {
-        return func(c context.Context, rw http.ResponseWriter, r *http.Request, params httprouter.Params) {
-                if err := UseConfig(&c); err != nil {
-                        log.WithError(err).Errorf(c, "Failed to install service configuration.")
-
-                        rw.WriteHeader(http.StatusInternalServerError)
-                        return
+func WithConfig() router.Handler {
+        return func(c *router.Context) {
+                if err := UseConfig(&c.Context); err != nil {
+                        log.WithError(err).Errorf(c.Context, "Failed to install service configuration.")
+                        c.Writer.WriteHeader(http.StatusInternalServerError)
+                        c.Abort()
                 }
-                h(c, rw, r, params)
         }
 }