Circumstances will oblige me to go.

I shall be obliged to go by the circumstances

I am obliged to go by the circumstances

I was obliged to go by the circumstances

I should be obliged to go by the circumstances

Explanation

Active Voice: Circumstances will oblige me to go.

Passive Voice: I shall be obliged to go by the circumstances.

Future Indefinite Tense

Active Voice Formula: Subject + Will/Shall + Verb (Ist form) + Object + (.)
Passive Voice Formula: Convert Object to Subject + Will/Shall + Be + Verb (3rd form) + By + Convert Subject to Object + Remaining + (.)