code: func (eg *EngineGroup) SetMaxIdleConns(conns int) {
  	eg.Engine.db.SetMaxIdleConns(conns)
  	for i := 0; i < len(eg.slaves); i++ {
  		eg.slaves[i].db.SetMaxIdleConns(conns)
  	}
  }
docs: // SetMaxIdleConns set the max idle connections on pool, default is 2