.NET 5 Azure Function (dotnet-isolated) - Input binding from keyvault

Question

I am trying to connect my function app to keyvault and get queue name and connection secrets. This was working well with .netcore3.1 app using the ConfigureAppConfiguration(IFunctionsConfigurationBuilder builder) method in FunctionStartup.

After upgrading to .net5 dotnet-isolated, the bindings does not work. I configured azurekeyvault in Program.cs but still it does not pick from keyvault. Seems like functionstartup is trying to bind before Main() is invoked.

QueueFunction

 public static void Run([QueueTrigger("%QueueName%", Connection = "QueueConnection")] string message, string id)

Startup.cs (.netcore3.1)- working

 public override void ConfigureAppConfiguration(IFunctionsConfigurationBuilder builder)
    {
        var azureKeyVaultURL = Environment.GetEnvironmentVariable("AzureKeyVaultURL");
        var azureKeyVaultADAppID = Environment.GetEnvironmentVariable("AzureKeyVaultMIAppID");


        builder.ConfigurationBuilder
                    .SetBasePath(Environment.CurrentDirectory)
                    .AddAzureKeyVault(new Uri(azureKeyVaultURL), new ManagedIdentityCredential(azureKeyVaultADAppID))
                    .AddEnvironmentVariables()
                .Build();
    }

Program.cs (.net5)- Not working

var host = new HostBuilder()
            .ConfigureFunctionsWorkerDefaults()
            .ConfigureAppConfiguration(config =>{
                 var azureKeyVaultURL = Environment.GetEnvironmentVariable("AzureKeyVaultURL");
                var azureKeyVaultADAppID = Environment.GetEnvironmentVariable("AzureKeyVaultMIAppID");

                config
                   .SetBasePath(Environment.CurrentDirectory)
                   .AddAzureKeyVault(new Uri(azureKeyVaultURL), new ManagedIdentityCredential(azureKeyVaultADAppID))
                   .AddEnvironmentVariables()
                .Build();
            })
.Build()