title: Angular: NullInjectorError: No provider for InjectionToken config
body: <p>I'm getting this error:</p>
  
  <pre><code>ERROR Error: Uncaught (in promise): NullInjectorError: StaticInjectorError(AppModule)[InjectionToken config]: 
    StaticInjectorError(Platform: core)[InjectionToken config]: 
      NullInjectorError: No provider for InjectionToken config!
  NullInjectorError: StaticInjectorError(AppModule)[InjectionToken config]: 
    StaticInjectorError(Platform: core)[InjectionToken config]: 
      NullInjectorError: No provider for InjectionToken config!
  </code></pre>
  
  <p>My module file already has <code>import { InjectionToken } from '@angular/core';</code> and has <code>InjectionToken</code> in the providers list. What could be causing this error? Does InjectionToken  rely on some other provider? This error message seems pretty useless.</p>