mongodb com.mongodb.async.client.clientsessionhelper未选择服务器错误

我想用scala连接mongodb,但出现错误: No server chosen by com.mongodb.async.client.ClientSessionHelper$1@8c3b9d from cluster description ClusterDescription{type=UNKNOWN, connectionMode=SINGLE, serverDescriptions=[ServerDescription{address=10.74.155.54:27017, type=UNKNOWN, state=CONNECTING}]}. Waiting for 30000 ms before timing out 以下是一些版本信息: -MongoDB:4.0.3版 -斯卡拉:2.11.12

这是我的 build.sbt 文件

libraryDependencies ++= Seq(
    "org.mongodb" % "bson" % "3.8.2",
    "org.mongodb" % "mongodb-driver-core" % "3.8.2",
    "org.mongodb" % "mongodb-driver-async" % "3.8.2",
    "org.mongodb.scala" %% "mongo-scala-driver" % "2.4.2",
    "org.mongodb.scala" % "mongo-scala-bson_2.11" % "2.4.2"
)

我这样编码:

val mongoClient: MongoClient =  MongoClient("mongodb://xxxx/mydb")
val database: MongoDatabase = mongoClient.getDatabase("mydb")
val collection: MongoCollection[Document] = database.getCollection("test")

我只想连接一个 standalone mongod ,你能帮我吗?

谢谢!