If the data you are fetching from config.json are just about a configuration of an application module and you are trying to create a Config service to store them, I think the best would be to assign it to the environment and read it in your Config service later. The environment is available in main.ts, so no hacking (createAppModule) needed.

import { environment } from './environments/environment';
import { AppModule } from './app/';

getHttp().get('/assets/config.json').toPromise()
   .then((res: Response) => {
       let conf = res.json();
       environment.settings = conf;
       platformBrowserDynamic().bootstrapModule(AppModule);
});

You must also declare all new properties of environment in your src/environments/environment.ts file.

The cli is attempting to use ahead of time compilation. Because of this, it needs to be able to find your main NgModule.

Usually the AOT compiler is able to do this statically just by looking for bootstrap calls. However you are not immediately bootstrapping, so the compiler needs you to explicitly tell it the name of your app module so it can compile it and all of it's components.

Solutions

ng eject and manually configure entryModule

The preferred solution is to tell the cli the name of your entryModule. This will allow AOT to work and give you all of it's benefits. However the cli does not currently support this(But there is a PR for adding an option #4077).

The current workaround is to use ng eject --aot to switch to a manual webpack based build. Then you can configure your entryModule directly.

1. ng eject --aot
2. Open webpack.config.js and search for new AotPlugin
   • Add the following and replace your AppModule name
     entryModule: 'path/to/app.module#AppModule'

Skip AOT

You can entirely skip this issue by using the --no-aot flag if you just need to get a build working. This isn't recommended as your app will be much slower and larger than it normally would(it will have to compile components at runtime and you will have to ship the compilier which is large).

ng prod --no-aot

The accepted answer didn't work for me. Extracting the bootstrapModule part will let Angular find the bootstrap code.

import { environment } from './environments/environment';
import { AppModule } from './app/';

const bootstrap = () => {
  platformBrowserDynamic().bootstrapModule(AppModule);
};

getHttp().get('/assets/config.json').toPromise()
    .then((res: Response) => {
       let conf = res.json();
       environment.settings = conf;
       bootstrap();
});