Following the configuration docs for my n8n docker instance I get an error
ERROR: In file ./.env: environment variable name ‘export WEBHOOK_TUNNEL_URL’ may not contain whitespace.
So I remove the whitespace and the .env file appears like this:
I can start n8n docker without error but when attempting to integrate Slack OAuth 2 API the OAuth Callback URL is http://localhost:5678/rest/oauth2-credential/callback
yes, it would appear the problem is with the space after export.
but manually exporting the environment variable I can set it… 
but still same OAuth Callback URL
After setting that do you restart n8n and also load again the editor-UI?
Correct. Stop the container, start container, wait and reload the UI.
Then your docker-setup must be wrong. I assume you do not tell docker to use that environment variable.
Is there a reason why you do not follow our guide?
In that one you will for example see that variables which are defined in the .env file get also set in the docker-compose.yml file so that docker knows that they should be used (you can see that for example with N8N_BASIC_AUTH_USER underneath environment).
I have two separate servers running Docker (server A is running Traefik and all the associated Cloudflare containers that automatically generate DNS entries for each subdomain and get certificates with Let’s Encrypt, etc.) and server B is running n8n.
Thanks for pointing that out! I was missing the environment setting in my docker-compose.
I did get the environment variable into my docker-compose and now the OAuth callback URL is updated but I am getting an error:
wow. I discovered I am terrible at following directions. I missed a step and that was what led to the error.
problem solved. thanks.
Glad to hear! Yes can also happen quite easily with a 19 step process 
Have fun!
