Create server side auth context lazily
diff --git a/src/cpp/server/server_context.cc b/src/cpp/server/server_context.cc
index 1bb3a8b..0be7713 100644
--- a/src/cpp/server/server_context.cc
+++ b/src/cpp/server/server_context.cc
@@ -153,4 +153,11 @@
   auth_context_ = CreateAuthContext(call);
 }
 
+std::shared_ptr<const AuthContext> ServerContext::auth_context() const {
+  if (auth_context_.get() == nullptr) {
+    auth_context_ = CreateAuthContext(call_);
+  }
+  return auth_context_;
+}
+
 }  // namespace grpc