INFO Waiting for ghost table to be migrated. Current lag is 0s

run command
` /Users/wilson/Downloads/gh-ost --allow-on-master --initially-drop-ghost-table --verbose --debug --throttle-flag-file="/Users/wilson/Downloads/a/1.log" --user="root" --password="1234" --host="localhost" --database="test" --table="news" --alter="ADD COLUMN abc1 varchar(10)" --switch-to-rbr --cut-over=default -ok-to-drop-table --execute`

then stucked？

the log like this

```
2019-07-26 17:50:30 INFO starting gh-ost 1.0.48
2019-07-26 17:50:30 INFO Migrating `test`.`news`
2019-07-26 17:50:30 INFO connection validated on localhost:3306
2019-07-26 17:50:30 INFO User has ALL privileges
2019-07-26 17:50:30 INFO binary logs validated on localhost:3306
2019-07-26 17:50:30 INFO Restarting replication on localhost:3306 to make sure binlog settings apply to replication thread
2019-07-26 17:50:30 INFO Inspector initiated on localhost:3306, version 5.7.16-log
2019-07-26 17:50:30 INFO Table found. Engine=InnoDB
2019-07-26 17:50:30 DEBUG Estimated number of rows via STATUS: 8
2019-07-26 17:50:30 DEBUG Validated no foreign keys exist on table
2019-07-26 17:50:30 DEBUG Validated no triggers exist on table
2019-07-26 17:50:30 INFO Estimated number of rows via EXPLAIN: 8
2019-07-26 17:50:30 DEBUG Potential unique keys in news: [PRIMARY (auto_increment): [id]; has nullable: false]
2019-07-26 17:50:30 INFO Recursively searching for replication master
2019-07-26 17:50:30 DEBUG Looking for master on localhost:3306
2019-07-26 17:50:30 INFO Master found to be localhost:3306
2019-07-26 17:50:30 WARNING log_slave_updates not found on localhost:3306, but executing directly on master, so I'm proceeding
2019-07-26 17:50:30 INFO connection validated on localhost:3306
2019-07-26 17:50:30 DEBUG Streamer binlog coordinates: mysql-bin.000004:154
2019-07-26 17:50:30 INFO Connecting binlog streamer at mysql-bin.000004:154
[2019/07/26 17:50:30] [info] binlogsyncer.go:133 create BinlogSyncer with config {99999 mysql localhost 3306 root false false false UTC true 0 0s 0s 0 false}
[2019/07/26 17:50:30] [info] binlogsyncer.go:354 begin to sync binlog from position (mysql-bin.000004, 154)
[2019/07/26 17:50:30] [info] binlogsyncer.go:203 register slave for master server localhost:3306
2019-07-26 17:50:30 DEBUG Beginning streaming
2019-07-26 17:50:30 INFO connection validated on localhost:3306
[2019/07/26 17:50:30] [info] binlogsyncer.go:723 rotate to (mysql-bin.000004, 154)
2019-07-26 17:50:30 INFO rotate to next log from mysql-bin.000004:0 to mysql-bin.000004
2019-07-26 17:50:30 INFO connection validated on localhost:3306
2019-07-26 17:50:30 INFO will use time_zone='SYSTEM' on applier
2019-07-26 17:50:30 INFO Examining table structure on applier
2019-07-26 17:50:30 INFO Applier initiated on localhost:3306, version 5.7.16-log
2019-07-26 17:50:30 INFO Dropping table `test`.`_news_gho`
2019-07-26 17:50:30 INFO Table dropped
2019-07-26 17:50:30 INFO Dropping table `test`.`_news_ghc`
2019-07-26 17:50:30 INFO Table dropped
2019-07-26 17:50:30 INFO Creating changelog table `test`.`_news_ghc`
2019-07-26 17:50:30 INFO Changelog table created
2019-07-26 17:50:30 INFO Creating ghost table `test`.`_news_gho`
2019-07-26 17:50:30 INFO Ghost table created
2019-07-26 17:50:30 INFO Altering ghost table `test`.`_news_gho`
2019-07-26 17:50:30 DEBUG ALTER statement: alter /* gh-ost */ table `test`.`_news_gho` ADD COLUMN abc1 varchar(10)
2019-07-26 17:50:30 INFO Ghost table altered
2019-07-26 17:50:30 INFO Waiting for ghost table to be migrated. Current lag is 0s
```