Docker Compose Configuration Standard

Manage secrets securely in Docker Compose by using a `.env` file to store sensitive information like database connection strings and API keys. The `.env` file must be added to `.gitignore` to prevent accidental exposure in version control.

The double-underscore convention maps environment variables to hierarchical ASP.NET Core configuration keys. Using `__` in your environment variable names correctly binds them to the .NET configuration system without requiring custom code prefixes.

Set up a `docker-compose.yml` file for a .NET microservice by defining your services and referencing variables from a `.env` file. You also need to create a `.env.example` file to document required variables and update `.gitignore` to exclude the actual `.env` file.

You should not use custom environment variable prefixes for ASP.NET Core configuration in Docker Compose. Relying on the standard double-underscore convention ensures correct configuration binding and prevents common mapping pitfalls.

Docker Compose works with PostgreSQL and .NET configuration binding by defining the PostgreSQL service in the `docker-compose.yml` file. You store the connection string in a `.env` file and map it to the .NET application using the double-underscore convention.

ASP.NET Core environment variables fail to bind correctly in Docker Compose when you do not use the double-underscore convention for hierarchical keys. Using custom prefixes in your code or failing to load the `.env` file also causes configuration mapping failures.