I am trying to configure docker to work with umbraco, nginx & mssql but all I get is 502 gateway. Upon inspection of the logs for umbraco, I see:

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible.

I am have all 3 services on the same network inside Umbraco with the mssql port exposed at 1433. I need some assistance to configure the correct connection string, and help with any other possible network issues. This is all local on a dev environment.