Implement JWT Token Authentication in program.cs file

Sure, here is a basic example of how you can implement JWT Token Authentication in a .NET Core application. This will be done in the Startup.cs file, not Program.cs.

1. First, you need to install the Microsoft.AspNetCore.Authentication.JwtBearer package. You can do this via the NuGet package manager or by running the following command in your Package Manager Console:

Install-Package Microsoft.AspNetCore.Authentication.JwtBearer

2. In your Startup.cs file, add the following code in the ConfigureServices method:

public void ConfigureServices(IServiceCollection services)
{
    services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
        .AddJwtBearer(options =>
        {
            options.TokenValidationParameters = new TokenValidationParameters
            {
                ValidateIssuer = true,
                ValidateAudience = true,
                ValidateLifetime = true,
                ValidateIssuerSigningKey = true,
                ValidIssuer = Configuration["Jwt:Issuer"],
                ValidAudience = Configuration["Jwt:Issuer"],
                IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(Configuration["Jwt:Key"]))
            };
        });

    services.AddControllers();
}

3. In the Configure method, ensure that the authentication middleware is added:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }

    app.UseRouting();

    app.UseAuthentication(); // This line ensures the authentication middleware is used
    app.UseAuthorization();

    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}

4. You need to add the JWT settings in your appsettings.json file:

"Jwt": {
    "Key": "YourSecretKey",
    "Issuer": "YourIssuer"
}

Please replace "YourSecretKey" and "YourIssuer" with your own values.

5. Now, you can protect your controllers or actions with the [Authorize] attribute.

Please note that this is a basic example. In a real-world application, you would need to secure your secret key and issuer, handle token expiration and refresh, and manage user credentials securely.