How can we store data in storage using Capacitor JS with Angular?

I read this documentation, which is capacitor JS provided

This is my code for storing the data in capacitor js.

/*
 * this function is used for the set Value
 */
async setUser(data: any) {
  await Preferences.set({
        key: 'value',
        value: JSON.stringify(data)
  });
}

/*
 * this function is used for the get-Value
 */
async getUser() {
  const user: any = await Preferences.get({ key: 'value' });
  this.UsersDetails = user.value;
}

This is working fine when my app is running in the background.
When I trash my app in the background and call for getUser(). It’s giving a null value. it’s not work.

Can anyone suggest if I am missing anything, or is there any other way available to Store the data in Capacitor JS?