Program.cs

using System;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;


namespace SwaggerDiff
{
 public class Program
 {
 public static void Main(string[] args)
 {
 // Check that all required env variables exist
 ValidateRequiredEnvVariables();

 // Create and run Web Service
 CreateHostBuilder(args).Build().Run();
 }

 private static void ValidateRequiredEnvVariables()
 {
 // Get required env variables for application to run
 string hostname = Environment.GetEnvironmentVariable("SWAGGER_DIFF_HOSTNAME");
 string apiVersion = Environment.GetEnvironmentVariable("SWAGGER_DIFF_API_VERSION");
 string serviceNames = Environment.GetEnvironmentVariable("SWAGGER_DIFF_SERVICENAMES");
 string slackWebhookUrl = Environment.GetEnvironmentVariable("SWAGGER_DIFF_SLACK_WEBHOOK");

 bool isMissingRequiredEnvironmentVariable = true;

 if (hostname == null)
 {
 Console.WriteLine("Missing required environment variable 'SWAGGER_DIFF_HOSTNAME'");
 }
 else if (apiVersion == null)
 {
 Console.WriteLine("Missing required environment variable 'SWAGGER_DIFF_API_VERSION'");
 }
 else if (serviceNames == null)
 {
 Console.WriteLine("Missing required environment variable 'SWAGGER_DIFF_SERVICENAMES'");
 }
 else if (slackWebhookUrl == null)
 {
 Console.WriteLine("Missing required environment variable 'SWAGGER_DIFF_SLACK_WEBHOOK'");
 }
 else 
 {
 isMissingRequiredEnvironmentVariable = false;
 }

 if (isMissingRequiredEnvironmentVariable) {
 // Close application
 Environment.Exit(1);
 }
 }

 public static IHostBuilder CreateHostBuilder(string[] args) =>
 Host.CreateDefaultBuilder(args)
 .ConfigureLogging(logging =>
 {
 logging.ClearProviders();
 logging.AddConsole();
 }
 )
 .ConfigureWebHostDefaults(webBuilder =>
 {
 webBuilder.UseStartup<Startup>();
 }
 );
 }
}