"Go" is the correct answer because it is used to form the subjunctive mood in the past.

Option "am going" is incorrect because it is in the present continuous form, which is used to describe an action that is currently in progress or scheduled to happen in the near future.

Option "would go" is incorrect because it is in the conditional form, which is used to describe an action that would happen in certain conditions or in the future.

Option "had gone" is incorrect because it is in the past perfect form, which is used to describe an action that was completed before another action or point in time in the past. Here it doesn't indicate that the action was completed before anything else.