Couchbase ArrayAppend error connection shut down

I am struggling with this Error:connection shut down
I create document ,first array is appending in couchbase document but when i try to append second time it gives me the error (connection shut down). Someone please help mw with this.
couchbase-version: Enterprise Edition 6.0.1 build 2037
_, err := bucket.Insert(docId,interface{}, 0)
if err != nil {
_, err := bucket.MutateIn(docId, 0, 0).ArrayAppend(“someArray”,interface{}, false).Execute()
if err != nil {
fmt.Println(“this is err”, err)