README.md: use context.Context instead of endpoint.Context in examples

diff --git a/README.md b/README.md
index 03f2ecc..7a7a816 100644
--- a/README.md
+++ b/README.md
@@ -79,7 +79,7 @@
 
 // List responds with a list of all greetings ordered by Date field.
 // Most recent greets come first.
-func (gs *GreetingService) List(c endpoints.Context, r *GreetingsListReq) (*GreetingsList, error) {
+func (gs *GreetingService) List(c context.Context, r *GreetingsListReq) (*GreetingsList, error) {
   if r.Limit <= 0 {
     r.Limit = 10
   }
@@ -101,7 +101,7 @@
 We can also define methods that don't require a response or a request.
 ```go
 // Add adds a greeting.
-func (gs *GreetingService) Add(c endpoints.Context, g *Greeting) error {
+func (gs *GreetingService) Add(c context.Context, g *Greeting) error {
     k := datastore.NewIncompleteKey(c, "Greeting", nil)
     _, err := datastore.Put(c, k, g)
     return err
@@ -112,7 +112,7 @@
 }
 
 // Count returns the number of greetings.
-func (gs *GreetingService) Count(c endpoints.Context) (*Count, error) {
+func (gs *GreetingService) Count(c context.Context) (*Count, error) {
     n, err := datastore.NewQuery("Greeting").Count(c)
     if err != nil {
         return nil, err