fix some typo (#677)

core/syncx/once.go

@@ -2,7 +2,7 @@ package syncx
 
 import "sync"
 
-// Once returns a func that guanartees fn can only called once.
+// Once returns a func that guarantees fn can only called once.
 func Once(fn func()) func() {
 	once := new(sync.Once)
 	return func() {