Add appengine/v2 memcache support (#75)

Author: faisalraja

cache.go

@@ -70,7 +70,7 @@ type Cacher interface {
 }
 
 // Item is the unit of Cacher gets and sets.
-// Taken from google.golang.org/appengine/memcache
+// Taken from google.golang.org/appengine/v2/memcache
 type Item struct {
 	// Key is the Item's key (250 bytes maximum).
 	Key string

cachers/memcache/memcache.go

@@ -3,8 +3,8 @@ package memcache
 import (
 	"context"
 
-	"google.golang.org/appengine"
-	"google.golang.org/appengine/memcache"
+	"google.golang.org/appengine/v2"
+	"google.golang.org/appengine/v2/memcache"
 
 	"github.com/qedus/nds/v2"
 )

go.mod

@@ -10,7 +10,7 @@ require (
 	go.opencensus.io v0.22.4
 	golang.org/x/sys v0.0.0-20200722175500-76b94024e4b6 // indirect
 	golang.org/x/tools v0.0.0-20200723000907-a7c6fd066f6d // indirect
-	google.golang.org/appengine v1.6.6
+	google.golang.org/appengine/v2 v2.0.1
 	google.golang.org/genproto v0.0.0-20200722002428-88e341933a54 // indirect
 )