fix golint issues in zrpc (#531)

zrpc/internal/clientinterceptors/timeoutinterceptor.go

@@ -8,6 +8,7 @@ import (
 	"google.golang.org/grpc"
 )
 
+// TimeoutInterceptor is an interceptor that controls timeout.
 func TimeoutInterceptor(timeout time.Duration) grpc.UnaryClientInterceptor {
 	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn,
 		invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {