diff --git a/td.go b/td.go
index 2d33afa..f6243bc 100644
--- a/td.go
+++ b/td.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log"
 	"math"
+	"sync"
 	"time"
 
 	"github.com/Arman92/go-tdlib"