Expected validator to return Promise or Observable

It means that you have to add multiple validators in array

.
Example:

With Error

profileFormGroup = {
  budget: [null, Validators.required, Validators.min(1)]
};

Above one throws error that validator to return Promise or Observable

Fix:

profileFormGroup = {
  budget: [null, [Validators.required, Validators.min(1)]]
};

Explanation:

In angular Reactive form validation done by using in-built validators which could given in array in 2nd postion, when multiple validators used.

FIELD_KEY: [INITIAL_VALUE, [LIST_OF_VALIDATORS]]