* and duplex calls where the timeout only applies to the initial setup.
   */
  fun timeoutEarlyExit() {
    check(!timeoutEarlyExit)
    timeoutEarlyExit = true
    timeout.exit()
  }

  fun upgradeToSocket() {
    timeoutEarlyExit()

    withLock {
      check(exchange != null)
      check(!socketSinkOpen && !socketSourceOpen)
      check(!requestBodyOpen)

        val followUp = followUpRequest(response, exchange, chain)

        if (followUp == null) {
          if (exchange != null && exchange.isDuplex) {
            call.timeoutEarlyExit()
          }
          closeActiveExchange = false
          call.eventListener.followUpDecision(call, response, null)
          return response
        }

        val followUpBody = followUp.body