Environment-Specific Angular Configuration - Add Injection Token

app.module.ts

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import { MY_API_BASE } from './my-api.service';
import { environment } from '../environments/environment';

@NgModule({
  declarations: [ AppComponent ],
  imports: [ BrowserModule ],
  providers: [
    { provide: MY_API_BASE, useValue: environment.apiAddress }
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

my-api.service.ts

export const MY_API_BASE = new InjectionToken<string>("My API Address");

@Injectable({ providedIn: "root" })
export class MyApiService {
  constructor(
    private http: HttpClient,
    @Inject(MY_API_BASE) private apiAddress: string
  ) {}

  getFoo(): Observable<any> {
    return this.http.get(`${this.apiAddress}/foo`);
  }
}