Startup.cs

public void ConfigureServices(IServiceCollection services)
{

    services.AddControllers();
    services.AddSwaggerGen(c =>
    {
        c.SwaggerDoc("v1", new OpenApiInfo { Title = "PostService", Version = "v1" });
    });

    services.AddDbContext<PostServiceContext>(options =>
         options.UseSqlite(@"Data Source=post.db"));
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env, PostServiceContext dbContext)
{
    if (env.IsDevelopment())
    {
        dbContext.Database.EnsureCreated
        ...