Protect against nil in Thrift WithConnContext option

Summary: Handle `nil` correctly. Needed downstream.

Reviewed By: podtserkovskiy

Differential Revision: D95653367

fbshipit-source-id: 47aeaaf39a52d76a43f201a3464335c215afc381

Author: echistyakov

third-party/thrift/src/thrift/lib/go/thrift/server_options.go

@@ -88,6 +88,9 @@ func WithNumWorkers(num int) ServerOption {
 // that specifies a function that modifies the context passed to procedures per connection.
 func WithConnContext(connContext ConnContextFunc) ServerOption {
 	return func(config *serverConfig) {
+		if connContext == nil {
+			return
+		}
 		config.connContext = func(ctx context.Context, conn net.Conn) context.Context {
 			ctx = WithConnInfo(ctx, conn)
 			return connContext(ctx, conn)

third-party/thrift/src/thrift/lib/go/thrift/server_options_test.go

@@ -61,6 +61,10 @@ func TestWithConnContext(t *testing.T) {
 	require.NotNil(t, defaultConfig.connContext)
 	defaultConfig.connContext(context.TODO(), dummyConn)
 
+	nilConfig := newServerConfig(WithConnContext(nil))
+	require.NotNil(t, nilConfig.connContext)
+	nilConfig.connContext(context.TODO(), dummyConn)
+
 	invoked := false
 	customConnContextFn := func(ctx context.Context, conn net.Conn) context.Context { invoked = true; return ctx }
 	customConfig := newServerConfig(WithConnContext(customConnContextFn))