How to whitelist a hostname? (Selfhost)

Hi, I'm new to Forem and I love it. But after I followed the document and installed forem with container Containerized setup with dip gem, and I started the forem by using dip rails s. Then the console shows [1] * Listening on http://0.0.0.0:3000, so I opened my own domain that resolved to the server and I met this:

So I tried to edit the .env file and restart the server also the forem, still the same. And I cannot find any other files related to the host configuration. So can I have some help here? And apoligize for my bad English.