Update README.md

Author: mrukas

README.md

@@ -91,12 +91,43 @@ public static IHostBuilder CreateHostBuilder(string[] args) =>
         {
             cfg.AddEncryptedAppSettings(crypter =>
             {
-                crypter.CertificatePath = "test-certificate.pfx";
+                crypter.CertificatePath = "cert.pfx";
                 crypter.KeysToDecrypt = new List<string> { "Nested:KeyToEncrypt" };
             });
         });
 ```
 
 As you can see enabling decryption is as simple as adding a line of code. You just need to specify the path to the certificate and the keys that should be decrypted.
 
-Notice that nested keys have to be separated with colons in this case, because this is the default way to access nested configuration properties in .NET Core ([Link](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/?view=aspnetcore-3.1#configuration-keys-and-values)).
+If you want to also use the environment specific appsettings files (appsettings.Development.json, appsettings.Production.json) please use the overloaded method to configure as shown below:
+
+```csharp
+public static IHostBuilder CreateHostBuilder(string[] args) =>
+    Host.CreateDefaultBuilder(args)
+        .ConfigureWebHostDefaults(webBuilder =>
+        {
+            webBuilder.UseStartup<Startup>();
+        })
+        .ConfigureAppConfiguration((hostingContext, cfg) =>
+        {
+            cfg.AddEncryptedAppSettings(hostingContext.HostingEnvironment, crypter =>
+            {
+                crypter.CertificatePath = "cert.pfx";
+                crypter.KeysToDecrypt = new List<string> { "Nested:KeyToEncrypt" };
+            });
+        });
+```
+Notice how to `HostingEnvironment` property of the `hostingContext` variable is used.
+
+Notice that nested keys have to be separated with colons in this case, because this is the default way to access nested configuration properties in .NET Core ([Link](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/?view=aspnetcore-3.1#configuration-keys-and-values)).
+
+## How to generate a certificate
+Certificates can be generated by using Openssl.
+An example certificate is already in the project and the encrypted string in the example appsettings files has been encrypted with it.
+To generate a certificate you could use the following commands:
+
+`openssl genrsa 2048 > private.key`
+
+`openssl req -new -x509 -nodes -sha1 -days 365 -key private.key > public.cer`
+
+`openssl pkcs12 -export -in public.cer -inkey private.key -out cert.pfx`