Docker Engine 18.09 から Build-time secrets という機能が使えるようになりました。この機能を使えば docker build するときに secrets (API key, credentials, etc) を安全に取り扱えるようになります。 Introducing Docker Engine 18.09 - Docker Blog Integrate secrets in your Dockerfile and pass them along in a safe way. These secrets do not end up stored in the final image nor are they included in the build cache calculations to avoid anyone from using the c