Make HTTP middleware easier to use

server/auth/db.go

Index: server/auth/db.go
diff --git a/server/auth/db.go b/server/auth/db.go
index 61ca54c985f49dedcc81ae1554443c862807a67e..e69f3d26f9ff504352a658e931bc0b7bc8b4909e 100644
--- a/server/auth/db.go
+++ b/server/auth/db.go
@@ -1,35 +1,33 @@
 // 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 auth
 
 import (
 	"errors"
 	"fmt"
 	"net"
-	"net/http"
 	"strings"
 	"time"
 
-	"github.com/julienschmidt/httprouter"
 	"golang.org/x/net/context"
 
 	"github.com/luci/luci-go/common/clock"
 	"github.com/luci/luci-go/common/lazyslot"
 	"github.com/luci/luci-go/common/logging"
 	"github.com/luci/luci-go/common/mathrand"
 
 	"github.com/luci/luci-go/server/auth/identity"
 	"github.com/luci/luci-go/server/auth/service/protocol"
-	"github.com/luci/luci-go/server/middleware"
+	"github.com/luci/luci-go/server/router"
 	"github.com/luci/luci-go/server/secrets"
 )
 
 // ErrNoDB is returned by default DB returned from GetDB if no DBFactory is
 // installed in the context.
 var ErrNoDB = errors.New("auth: using default auth.DB, install a properly mocked one instead")
 
 // DB is interface to access a database of authorization related information.
 //
 // It is static read only object that represent snapshot of auth data at some
@@ -79,24 +77,25 @@ type DBCacheUpdater func(c context.Context, prev DB) (DB, error)
 
 // dbKey is used for context.Context key of DBFactory.
 type dbKey int
 
 // UseDB sets a factory that creates DB instances.
 func UseDB(c context.Context, f DBFactory) context.Context {
 	return context.WithValue(c, dbKey(0), f)
 }
 
 // WithDB is middleware that sets given DBFactory in the context before calling
-// a handler.
-func WithDB(h middleware.Handler, f DBFactory) middleware.Handler {
-	return func(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
-		h(UseDB(c, f), rw, r, p)
+// the next handler.
+func WithDB(f DBFactory) router.Middleware {
+	return func(c *router.Context, next router.Handler) {
+		c.Context = UseDB(c.Context, f)
+		next(c)
 	}
 }
 
 // GetDB returns most recent snapshot of authorization database using factory
 // installed in the context via `UseDB`.
 //
 // If no factory is installed, returns DB that forbids everything and logs
 // errors. It is often good enough for unit tests that do not care about
 // authorization, and still not horribly bad if accidentally used in production.
 //