I thought it would make sense to pass the env[:request_headers] to some IntraProcessTraceId method or 
```
def self.current(headers = nil)
  # Maybe some more involved logic about what could qualify as possible TRACEID headers or Thread vars
  #
  headers['X-B3-Traceid'] ? headers['X-B3-Traceid'] ? Thread.current['TRACEID']
end
```

To ensure that if the header is existing in the request it is persisted. 

I'm not actually sure where Thread.current['TRACEID'] is actually being set in the Faraday middleware as it stands alone unless it only meant to be used in compliment with the rack middleware.