s.SqlStore.GetMaster().BeginTx undefined

```
$ go version
go version go1.16.2 linux/amd64
$ go get -u github.com/mattermost/mmetl
# github.com/mattermost/mattermost-server/v5/store/sqlstore
gocode/pkg/mod/github.com/mattermost/mattermost-server/v5@v5.33.2/store/sqlstore/system_store.go:120:26: s.SqlStore.GetMaster().BeginTx undefined (type *gorp.DbMap has no field or method BeginTx)

```