using a function that calls observable with 3 different observables associated with a switch map results in an error

try to add return before this.http.get(environment.public_generate_presigned_url_resource)

it should be like this

 publicresourceuploadtos3(event): Observable<any>{
    console.log('the service at least ran');

    const mediatobeuploaded = event.target.files[0];
   return this.http.get(environment.public_generate_presigned_url_resource).pipe(
      switchMap((req : any)=>{
        console.log('did the call to the server');

        const resourceurl = req.uriroot + req.fields.key;

        let fd = new FormData();
        fd.append('acl', req.fields.acl);
        fd.append('key', req.fields.key);
        fd.append('content-type', req.fields['content-type']);
        fd.append('policy', req.fields.policy);
        fd.append('x-amz-algorithm', req.fields['x-amz-algorithm']);
        fd.append('x-amz-credential', req.fields['x-amz-credential']);
        fd.append('x-amz-date', req.fields['x-amz-date']);
        fd.append('x-amz-signature', req.fields['x-amz-signature']);
        fd.append('file', mediatobeuploaded);
        this.http.post(req.url, fd).pipe(
          switchMap((req2: any)=>{
            const result = {
              resourceurl : resourceurl,
              resourcekey: req.fields.key
            };
            return of(result);


        }));


      }));


  }