function onHttp2SessionGoAway (errorCode) {
  ...

  // Fail head of pipeline.
  console.log('clinet[kRunningIdx]:', clinet[kRunningIdx])  // clinet[kRunningIdx]: 2
  console.log('clinet[kPendingIdx]:', clinet[kPendingIdx])  // clinet[kPendingIdx]: 2
  console.log('clinet[kQueue].length:', clinet[kQueue].length)  // clinet[kQueue].length: 2
  console.log('clinet[kQueue]:', clinet[kQueue])  // clinet[kQueue]: [null, null]
  
  const request = client[kQueue][client[kRunningIdx]]
  client[kQueue][client[kRunningIdx]++] = null
  util.errorRequest(client, request, err)  // throws "Cannot read properties of undefined"
  client[kPendingIdx] = client[kRunningIdx]

  assert(client[kRunning] === 0)

  ...
}