问ionic 4-背景地理位置问题

EN

setBackgroundTracking(){
    this.backgroundGeolocation.configure(config)
          .then(() => {

            this.backgroundGeolocation.on('location').subscribe((location: BackgroundGeolocationResponse) => {
              console.log(location);

              // IMPORTANT:  You must execute the finish method here to inform the native plugin that you're finished,
              // and the background-task may be completed.  You must do this regardless if your operations are successful or not.
              // IF YOU DON'T, ios will CRASH YOUR APP for spending too much time in the background.
              this.backgroundGeolocation.finish(); // FOR IOS ONLY
            });

          });


The above code is an exact copy paste from the documentation. and the code is buggy.

Property 'subscribe' does not exist on type 'Promise<any>'.ts(2339)

If you guys can fix the code or tell me another way to do it, please let me know. I have just been brainstorming would appreciate input/