title: mongodb No server chosen by com.mongodb.async.client.ClientSessionHelper error
body: <p>I want to connect mongodb by use scala , but I got error: <code>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
  </code>
  Here is some version info:
  - mongodb: 4.0.3
  - scala: 2.11.12</p>
  
  <p>This is my <code>build.sbt</code> file</p>
  
  <pre><code>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"
  )
  </code></pre>
  
  <p>I code like this:</p>
  
  <pre><code>val mongoClient: MongoClient =  MongoClient("mongodb://xxxx/mydb")
  val database: MongoDatabase = mongoClient.getDatabase("mydb")
  val collection: MongoCollection[Document] = database.getCollection("test")
  </code></pre>
  
  <p>I just want to connect a <code>standalone mongod</code>, Can you help me?</p>
  
  <p>Thanks!</p>