Observable and RxJS (POST)

Post request in Service

getCollegeList(dataJson: string) {
    const model: Subject = new Subject();
    this.http.post(this.API_URL + "/cs/searchByMarks",dataJson,{'headers':this.headers}).subscribe((res) => {
      // console.log(res);
      model.next({data:res})
    });
    console.log(model)
    return model
  }

Getting results in Component

sendSubjectDetails() {
    console.log("on submit")
    const data = this.subjectForm.value;
    const dataJson = JSON.stringify(data)
    console.log(dataJson)
    this.service.getCollegeList(dataJson).subscribe((res) => {
      console.log(res.data);
    });
    // this.service.getCollegeList(dataJson);
  }

Headers in Service

API_URL = environment.apiUrl;
  headers = { 'content-type': 'application/json'}