Rails Not able to access headers after moving to Digital Ocean - ruby-on-rails

Question

I have a rails app that serves the web and an Android client. I recently upgraded to Ruby 2.0 from 1.9.3. I went to do some work on the Android client and kept getting status 500 from the API. I return JSON data for each user by sending their auth_token in the headers.
I checked the server logs to see what was up. This method was returning nil:
def api_user
my_auth = request.headers["auth_token"]
api_user = User.where(authentication_token: my_auth).first
end
I hadn't touched my Android client so I knew the problem wasn't there.
I tried curl --header "auth_token: xxxxxxxxxxxxxxxxxxxx" https://myapp.com/api/etc.json
And got status 500 as well.
I recently made a bunch of changes to the rails app and moved from Heroku to Digial Ocean, so I figured that maybe I'd messed something up in the process. I tried locally:
curl --header "auth_token: xxxxxxxxxxxxxxxxxxxx" http://localhost:3000/api/etc.json
And it returned data for the specified user!
I'm really confused. I tried logging in production to see if the headers were there at all:
Rails.logger.info "auth_token #{request.headers["auth_token"]}"
In development this produced auth_token xxxxxxxxxxxxxxxx as it should.
In production this returned auth_token. So I'm not able to access the headers in production. Why is this?
Setup info: unicorn on a DigitalOcean droplet running Dokku. Let me know if you need more info - I'm really stumped....
ADDITIONAL INFO
Procfile
web: bundle exec unicorn -p $PORT -c ./config/unicorn.rb
worker: bundle exec rake jobs:work
config unicorn.rb
worker_processes 3
timeout 3000
preload_app true
before_fork do |server, worker|
Signal.trap 'TERM' do
puts 'Unicorn master intercepting TERM and sending myself QUIT instead'
Process.kill 'QUIT', Process.pid
end
defined?(ActiveRecord::Base) and
ActiveRecord::Base.connection.disconnect!
end
after_fork do |server, worker|
Signal.trap 'TERM' do
puts 'Unicorn worker intercepting TERM and doing nothing. Wait for master to send QUIT'
end
defined?(ActiveRecord::Base) and
ActiveRecord::Base.establish_connection
end

Answer 1

Okay, this ended up being something related to nginx. I found the answer here.
Basically, you have to add the line below to your nginx.conf file right after http {to use underscores in headers.
underscores_in_headers on;
It works.