diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go
index ea3738b..407d933 100644
--- a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go
@@ -16,22 +16,41 @@
 // Execution is done in left-to-right order, including passing of context.
 // For example ChainUnaryServer(one, two, three) will execute one before two before three, and three
 // will see context changes of one and two.
+//
+// While this can be useful in some scenarios, it is generally advisable to use google.golang.org/grpc.ChainUnaryInterceptor directly.
 func ChainUnaryServer(interceptors ...grpc.UnaryServerInterceptor) grpc.UnaryServerInterceptor {
 	n := len(interceptors)
 
+	// Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	if n == 0 {
+		return func(ctx context.Context, req interface{}, _ *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+			return handler(ctx, req)
+		}
+	}
+
+	// The degenerate case, just return the single wrapped interceptor directly.
+	if n == 1 {
+		return interceptors[0]
+	}
+
+	// Return a function which satisfies the interceptor interface, and which is
+	// a closure over the given list of interceptors to be chained.
 	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
-		chainer := func(currentInter grpc.UnaryServerInterceptor, currentHandler grpc.UnaryHandler) grpc.UnaryHandler {
-			return func(currentCtx context.Context, currentReq interface{}) (interface{}, error) {
-				return currentInter(currentCtx, currentReq, info, currentHandler)
+		currHandler := handler
+		// Iterate backwards through all interceptors except the first (outermost).
+		// Wrap each one in a function which satisfies the handler interface, but
+		// is also a closure over the `info` and `handler` parameters. Then pass
+		// each pseudo-handler to the next outer interceptor as the handler to be called.
+		for i := n - 1; i > 0; i-- {
+			// Rebind to loop-local vars so they can be closed over.
+			innerHandler, i := currHandler, i
+			currHandler = func(currentCtx context.Context, currentReq interface{}) (interface{}, error) {
+				return interceptors[i](currentCtx, currentReq, info, innerHandler)
 			}
 		}
-
-		chainedHandler := handler
-		for i := n - 1; i >= 0; i-- {
-			chainedHandler = chainer(interceptors[i], chainedHandler)
-		}
-
-		return chainedHandler(ctx, req)
+		// Finally return the result of calling the outermost interceptor with the
+		// outermost pseudo-handler created above as its handler.
+		return interceptors[0](ctx, req, info, currHandler)
 	}
 }
 
@@ -40,22 +59,31 @@
 // Execution is done in left-to-right order, including passing of context.
 // For example ChainUnaryServer(one, two, three) will execute one before two before three.
 // If you want to pass context between interceptors, use WrapServerStream.
+//
+// While this can be useful in some scenarios, it is generally advisable to use google.golang.org/grpc.ChainStreamInterceptor directly.
 func ChainStreamServer(interceptors ...grpc.StreamServerInterceptor) grpc.StreamServerInterceptor {
 	n := len(interceptors)
 
-	return func(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
-		chainer := func(currentInter grpc.StreamServerInterceptor, currentHandler grpc.StreamHandler) grpc.StreamHandler {
-			return func(currentSrv interface{}, currentStream grpc.ServerStream) error {
-				return currentInter(currentSrv, currentStream, info, currentHandler)
+	// Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	if n == 0 {
+		return func(srv interface{}, stream grpc.ServerStream, _ *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+			return handler(srv, stream)
+		}
+	}
+
+	if n == 1 {
+		return interceptors[0]
+	}
+
+	return func(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+		currHandler := handler
+		for i := n - 1; i > 0; i-- {
+			innerHandler, i := currHandler, i
+			currHandler = func(currentSrv interface{}, currentStream grpc.ServerStream) error {
+				return interceptors[i](currentSrv, currentStream, info, innerHandler)
 			}
 		}
-
-		chainedHandler := handler
-		for i := n - 1; i >= 0; i-- {
-			chainedHandler = chainer(interceptors[i], chainedHandler)
-		}
-
-		return chainedHandler(srv, ss)
+		return interceptors[0](srv, stream, info, currHandler)
 	}
 }
 
@@ -66,19 +94,26 @@
 func ChainUnaryClient(interceptors ...grpc.UnaryClientInterceptor) grpc.UnaryClientInterceptor {
 	n := len(interceptors)
 
+	// Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	if n == 0 {
+		return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+			return invoker(ctx, method, req, reply, cc, opts...)
+		}
+	}
+
+	if n == 1 {
+		return interceptors[0]
+	}
+
 	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
-		chainer := func(currentInter grpc.UnaryClientInterceptor, currentInvoker grpc.UnaryInvoker) grpc.UnaryInvoker {
-			return func(currentCtx context.Context, currentMethod string, currentReq, currentRepl interface{}, currentConn *grpc.ClientConn, currentOpts ...grpc.CallOption) error {
-				return currentInter(currentCtx, currentMethod, currentReq, currentRepl, currentConn, currentInvoker, currentOpts...)
+		currInvoker := invoker
+		for i := n - 1; i > 0; i-- {
+			innerInvoker, i := currInvoker, i
+			currInvoker = func(currentCtx context.Context, currentMethod string, currentReq, currentRepl interface{}, currentConn *grpc.ClientConn, currentOpts ...grpc.CallOption) error {
+				return interceptors[i](currentCtx, currentMethod, currentReq, currentRepl, currentConn, innerInvoker, currentOpts...)
 			}
 		}
-
-		chainedInvoker := invoker
-		for i := n - 1; i >= 0; i-- {
-			chainedInvoker = chainer(interceptors[i], chainedInvoker)
-		}
-
-		return chainedInvoker(ctx, method, req, reply, cc, opts...)
+		return interceptors[0](ctx, method, req, reply, cc, currInvoker, opts...)
 	}
 }
 
@@ -89,19 +124,26 @@
 func ChainStreamClient(interceptors ...grpc.StreamClientInterceptor) grpc.StreamClientInterceptor {
 	n := len(interceptors)
 
+	// Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	if n == 0 {
+		return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
+			return streamer(ctx, desc, cc, method, opts...)
+		}
+	}
+
+	if n == 1 {
+		return interceptors[0]
+	}
+
 	return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
-		chainer := func(currentInter grpc.StreamClientInterceptor, currentStreamer grpc.Streamer) grpc.Streamer {
-			return func(currentCtx context.Context, currentDesc *grpc.StreamDesc, currentConn *grpc.ClientConn, currentMethod string, currentOpts ...grpc.CallOption) (grpc.ClientStream, error) {
-				return currentInter(currentCtx, currentDesc, currentConn, currentMethod, currentStreamer, currentOpts...)
+		currStreamer := streamer
+		for i := n - 1; i > 0; i-- {
+			innerStreamer, i := currStreamer, i
+			currStreamer = func(currentCtx context.Context, currentDesc *grpc.StreamDesc, currentConn *grpc.ClientConn, currentMethod string, currentOpts ...grpc.CallOption) (grpc.ClientStream, error) {
+				return interceptors[i](currentCtx, currentDesc, currentConn, currentMethod, innerStreamer, currentOpts...)
 			}
 		}
-
-		chainedStreamer := streamer
-		for i := n - 1; i >= 0; i-- {
-			chainedStreamer = chainer(interceptors[i], chainedStreamer)
-		}
-
-		return chainedStreamer(ctx, desc, cc, method, opts...)
+		return interceptors[0](ctx, desc, cc, method, currStreamer, opts...)
 	}
 }
 
@@ -109,12 +151,16 @@
 //
 // WithUnaryServerChain is a grpc.Server config option that accepts multiple unary interceptors.
 // Basically syntactic sugar.
+//
+// Deprecated: use google.golang.org/grpc.ChainUnaryInterceptor instead.
 func WithUnaryServerChain(interceptors ...grpc.UnaryServerInterceptor) grpc.ServerOption {
-	return grpc.UnaryInterceptor(ChainUnaryServer(interceptors...))
+	return grpc.ChainUnaryInterceptor(interceptors...)
 }
 
 // WithStreamServerChain is a grpc.Server config option that accepts multiple stream interceptors.
 // Basically syntactic sugar.
+//
+// Deprecated: use google.golang.org/grpc.ChainStreamInterceptor instead.
 func WithStreamServerChain(interceptors ...grpc.StreamServerInterceptor) grpc.ServerOption {
-	return grpc.StreamInterceptor(ChainStreamServer(interceptors...))
+	return grpc.ChainStreamInterceptor(interceptors...)
 }