How to use a non-existent setting in Docker Spotify (sysctl example)

ExtendedHostConfig.scala

import com.google.common.collect.ImmutableMap
import com.spotify.docker.client.messages.HostConfig
import com.spotify.docker.client.shaded.com.fasterxml.jackson.annotation.JsonProperty

class ExtendedHostConfig(h: HostConfig) extends HostConfig {
  @JsonProperty("Sysctls")
  def sysctls(): ImmutableMap[String, String] = ImmutableMap.of(
    "net.ipv4.tcp_keepalive_time", "15",
    "net.ipv4.tcp_keepalive_intvl", "5",
    "net.ipv4.tcp_keepalive_probes", "3"
  )

  override def capAdd() = h.capAdd()

  override def blkioDeviceReadBps() = h.blkioDeviceReadBps()

  override def publishAllPorts() = h.publishAllPorts()

  override def oomScoreAdj() = h.oomScoreAdj()

  override def storageOpt() = h.storageOpt()

  override def pidsLimit() = h.pidsLimit()

  override def devices() = h.devices()

  override def cgroupParent() = h.cgroupParent()

  override def blkioDeviceReadIOps() = h.blkioDeviceReadIOps()

  override def readonlyRootfs() = h.readonlyRootfs()

  override def cpuPeriod() = h.cpuPeriod()

  override def extraHosts() = h.extraHosts()

  override def restartPolicy() = h.restartPolicy()

  override def containerIdFile() = h.containerIdFile()

  override def nanoCpus() = h.nanoCpus()

  override def blkioWeightDevice() = h.blkioWeightDevice()

  override def cpuQuota() = h.cpuQuota()

  override def memoryReservation() = h.memoryReservation()

  override def cpusetCpus() = h.cpusetCpus()

  override def links() = h.links()

  override def binds() = h.binds()

  override def volumesFrom() = h.volumesFrom()

  override def securityOpt() = h.securityOpt()

  override def dns() = h.dns()

  override def toBuilder = h.toBuilder

  override def oomKillDisable() = h.oomKillDisable()

  override def memorySwap() = h.memorySwap()

  override def portBindings() = h.portBindings()

  override def blkioWeight() = h.blkioWeight()

  override def memorySwappiness() = h.memorySwappiness()

  override def ipcMode() = h.ipcMode()

  override def dnsOptions() = h.dnsOptions()

  override def privileged() = h.privileged()

  override def shmSize() = h.shmSize()

  override def blkioDeviceWriteBps() = h.blkioDeviceWriteBps()

  override def memory() = h.memory()

  override def autoRemove() = h.autoRemove()

  override def pidMode() = h.pidMode()

  override def dnsSearch() = h.dnsSearch()

  override def cpusetMems() = h.cpusetMems()

  override def ulimits() = h.ulimits()

  override def blkioDeviceWriteIOps() = h.blkioDeviceWriteIOps()

  override def lxcConf() = h.lxcConf()

  override def tmpfs() = h.tmpfs()

  override def logConfig() = h.logConfig()

  override def networkMode() = h.networkMode()

  override def cpuShares() = h.cpuShares()

  override def capDrop() = h.capDrop()
}

Main.scala

val containerConfig = ContainerConfig.builder()
  .image("…")
  .hostConfig(new ExtendedHostConfig(hostConfig))
  .build()