Complete task in Action without awaiting - task gets cancelled - asp.net-core

Question

I have an async action, that completes a task that i need to wait for, before returning response to the cliend, but also a task that a want to run, but i don't care about the result.
[HttpPost]
[Route("api/update")]
public async Task Update(Competence competence)
{
await _competenceService.Update(competence);
_userService.DoNotWaitForMe(competence.Year);
}
Both _competenceService and _userService classes are injected into controller as Scoped via DI and both its methods are awaitable. I also use Entity framework and inject context class
// Startup.cs
services.AddScoped<ICompetenceService, CompetenceService>();
services.AddScoped<IUserService, UserService>();
services.AddDbContext<DbContext>(options =>
{
options.UseSqlServer(Configuration.GetConnectionString("DbContext"));
});
// CompetenceService.cs
async Task Update(Competence competence)
// UserService.cs
async Task DoNotWaitForMe(int Year)
While the awaited Update method completes as expected (or throws Exception on exception), the later never finishes, and throws exception
System.Threading.Tasks.TaskCanceledException: A task was canceled. at
Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenDbConnectionAsync(Boolean
errorsExpected, CancellationToken cancellationToken) at
Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenDbConnectionAsync(Boolean
errorsExpected, CancellationToken cancellationToken) at
Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenAsync(CancellationToken
cancellationToken, Boolean errorsExpected) at
Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject
parameterObject, CancellationToken cancellationToken) at
Microsoft.EntityFrameworkCore.Query.RelationalShapedQueryCompilingExpressionVisitor.AsyncQueryingEnumerable1.AsyncEnumerator.MoveNextAsync()
at
Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToListAsync[TSource](IQueryable1
source, CancellationToken cancellationToken) at
Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToListAsync[TSource](IQueryable`1
source, CancellationToken cancellationToken)
and sometimes also
System.ObjectDisposedException: Cannot access a disposed object. A
common cause of this error is disposing a context that was resolved
from dependency injection and then later trying to use the same
context instance elsewhere in your application. This may occur if you
are calling Dispose() on the context, or wrapping the context in a
using statement. If you are using dependency injection, you should
let the dependency injection container take care of disposing context
instances.
I would like to prevent DI (or whatever is responsible) from cancelling the Task, and disposing all the objects untill this async task is completed. Is there any way?

Answer 1

Simply, you can't just not await the task. The EF context has a scoped lifetime: it's instantiated when the request starts and disposed when the request finishes. If you return the response, before the work being done on the context is finished, then the context will be disposed, and an ObjectDisposedException will be thrown.
It's pretty much always wrong to not await tasks, especially in a web app. It is not the same as backgrounding. If you want to do something in the background, then you need to schedule it on an actual background service. That could be anything really: a separate process, a console app, an Azure Function, or a hosted service. The long and short is that you need to do the work on something actually intended to process tasks in the background, not just fire-and-forget a task.