Make HTTP middleware easier to use

appengine/logdog/coordinator/config/middleware.go

Index: appengine/logdog/coordinator/config/middleware.go
diff --git a/appengine/logdog/coordinator/config/middleware.go b/appengine/logdog/coordinator/config/middleware.go
index bef79ceb81eb25e0a01bd82e23f4f04587b2c900..fd4114db09c2835568765e6c67ec72e6b20b89d7 100644
--- a/appengine/logdog/coordinator/config/middleware.go
+++ b/appengine/logdog/coordinator/config/middleware.go
@@ -7,22 +7,18 @@ 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)
 	}
 }