When we did a .net core service we found that the appsettings.json was not read and hence the variable we null. If your normal configuration builder is as below,

var builder = new ConfigurationBuilder()

.SetBasePath(Directory.GetCurrentDirectory())

.AddJsonFile(“appsettings.json”, optional: true, reloadOnChange: true);

replace the same with

var builder = new ConfigurationBuilder()

.SetBasePath(System.AppDomain.CurrentDomain.BaseDirectory)

.AddJsonFile(“appsettings.json”, optional: true, reloadOnChange: true);

and give it a try. Sorry I could find that in the your code in a quick glance to show the exact location.