Following this article: https://andrewlock.net/injecting-services-into-validationattributes-in-asp-net-core/

When creating custom ValidationAttribute several people already note that is impossible to access/get any service from the GetService method inside the ValidationContext class, ServiceContainer property. Looking into the code is possible to see:

 var context = new ValidationContext( instance: container ?? validationContext.Model, serviceProvider: validationContext.ActionContext?.HttpContext?.RequestServices, items: null) { DisplayName = metadata.GetDisplayName(), MemberName = memberName }; 

https://github.com/aspnet/Mvc/blob/760c8f38678118734399c58c2dac981ea6e47046/src/Microsoft.AspNetCore.Mvc.DataAnnotations/Internal/DataAnnotationsModelValidator.cs

Since the ActionContext was obsolete: https://stackoverflow.com/questions/37286530/actioncontext-gone-in-microsoft-aspnetcore-mvc-controller - The service provider for a validation attribute is always null or empty. Let's make the ValidationAttribute great again, please fix this issue in the next patch.