How to Troubleshoot Angular HTTP Headers and Go CORS Issues?

Troubleshooting Angular HTTP Headers and Go CORS

CORS (Cross-Origin Resource Sharing) is often a source of headaches when connecting Angular apps to Go APIs. Understanding how to add Authorization headers in Angular and handling CORS in Go is crucial for successful communication between the two.

Angular Authorization Headers

To add Authorization headers in Angular, you should utilize Http Interceptors. An example of an Auth Interceptor is:

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    req = req.clone({
      setHeaders: {
        'Content-Type': 'application/json; charset=utf-8',
        'Accept': 'application/json',
        'Authorization': `Bearer ${AuthService.getToken()}`,
      },
    });
    return next.handle(req);
  }
}

Register the interceptor in your app's module:

providers: [
  {
    provide : HTTP_INTERCEPTORS,
    useClass: AuthInterceptor,
    multi   : true,
  },
],

Go CORS Handling

Ensure that your Go code allows the necessary request headers from the Angular app:

headersOk := handlers.AllowedHeaders([]string{"*"})
originsOk := handlers.AllowedOrigins([]string{"*"})
methodsOk := handlers.AllowedMethods([]string{"GET", "HEAD", "POST", "PUT", "OPTIONS"})

If issues persist, carefully configure your CORS settings to match the client's request headers.

Example of Resolved Issue

The following Angular code:

this.http.get<ProjectedBalance>(requestUrl, {headers: new HttpHeaders().set('Authorization', 'my-auth-token')})

Combined with the following Go code:

headersOk := handlers.AllowedHeaders([]string{"Authorization"})
originsOk := handlers.AllowedOrigins([]string{"*"})
methodsOk := handlers.AllowedMethods([]string{"GET", "HEAD", "POST", "PUT", "OPTIONS"})

Should successfully establish communication between the Angular app and Go API.

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