server/src/Core/Utilities/HostBuilderExtensions.cs

using System;
using System.Reflection;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;

namespace Bit.Core.Utilities
{
    public static class HostBuilderExtensions
    {
        public static IHostBuilder ConfigureCustomAppConfiguration(this IHostBuilder hostBuilder, string[] args)
        {
            // Reload app configuration with SelfHosted overrides.
            return hostBuilder.ConfigureAppConfiguration((hostingContext, config) =>
            {
                if (Environment.GetEnvironmentVariable("globalSettings__selfHosted")?.ToLower() != "true")
                {
                    return;
                }

                var env = hostingContext.HostingEnvironment;

                config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                    .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true)
                    .AddJsonFile("appsettings.SelfHosted.json", optional: true, reloadOnChange: true);

                if (env.IsDevelopment())
                {
                    var appAssembly = Assembly.Load(new AssemblyName(env.ApplicationName));
                    if (appAssembly != null)
                    {
                        config.AddUserSecrets(appAssembly, optional: true);
                    }
                }

                config.AddEnvironmentVariables();

                if (args != null)
                {
                    config.AddCommandLine(args);
                }
            });
        }
    }
}