Startup.cs

public class Startup
{
    private readonly IWebHostEnvironment _environment;

    public Startup(IWebHostEnvironment environment)
    {
        _environment = environment;
    }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers()
            .AddJsonOptions(options => options.JsonSerializerOptions.WriteIndented = _environment.IsDevelopment());
    }

    // Other code ommitted for brevity
}