Dependency Injection in ASP.NET Core and issue with null suppresion

builder.Services.AddDbContext<AppDb>();
builder.Services.AddHostedService(provider =>
    new DbMigrator(provider.GetService<ILogger<DbMigrator>>()!, provider.GetService<AppDb>()!)
);

Cannot resolve scoped service 'RemoteGatewayManager.Types.Classes.AppDb' from root provider

builder.Services.AddDbContext<AppDb>();
builder.Services.AddHostedService(provider =>
    new DbMigrator(provider.GetService<ILogger<DbMigrator>>()!, provider.GetService<AppDb>()!)
);

provider.GetService<AppDb>()!