@ngeth in your component

app.component.ts

import { Component, OnInit } from '@angular/core';
import { Eth } from '@ngeth/provider';
import { Observable } from 'rxjs';

@Component({
  selector: 'app-root',
  template: '<h1>Current Block : {{ block$ | async }}</h1>',
  styles: []
})
export class AppComponent implements OnInit {

  public block$: Observable<string>;

  constructor(private eth: Eth) {}

  ngOnInit() {
    this.block$ = this.eth.getBlockNumber();
  }
}