> If I wanted to explain to an English-speaking colleague why I can't attend a meeting later today, ... English grammar would oblige me to say 'I will go, am go

> If I wanted to explain to an English-speaking colleague why I can't attend a meeting later today, ... English grammar would oblige me to say 'I will go, am going, or have to go to a seminar'. There's also "I'm to go to a seminar".