code: function requestId (ctx, next) {
    let requestId = uuid.v4()
  
    ctx.id = requestId
    ctx.request.id = requestId
    ctx.state.requestId = requestId
    ctx.set('X-Request-Id', requestId)
  
    return next()
  }
docs: Generates a unique request ID for all requests, setting it as `ctx.id`, `ctx.request.id` and
  `ctx.state.requestId`. It will also set the `X-Request-Id` header to aid clients with debugging.
  
  @example
  ctx.headers
  // { `x-request-id`: '72243aca-e4bb-4a3a-a2e7-ed380c256826' }
  
  ctx.state
  // { requestId: '72243aca-e4bb-4a3a-a2e7-ed380c256826' }
  
  @returns {Promise}