HostedService StartAsync Block Fix

TL;DR

Don't await long tasks in StartAsync. Fire and forget or use BackgroundService.

The Error

App hangs on startup. Never reaches app.Run()

Root Cause

IHostedService.StartAsync must return quickly. You're doing await LongInit()

Fix

public Task StartAsync(CancellationToken ct)
{
    _ = Task.Run(() => LongInit(), ct);
    return Task.CompletedTask;
}

Or inherit BackgroundService and use ExecuteAsync.