Field service is not a command.
When Jesus said "Go forth and make disciples" he was not giving a command. He gave no commands, that was not his style.
The disciples were wondering what to do. They traveled with him for 3.5 years, he died like he did, he was resurrected and appeared to many. They wondered, 'Now what' by asking if he was going to restore the kingdom to them at that time, thinking the kingdom was earthly. (They didn't know about the gentile times ending in 1880 more years). As Jesus ascended he told them that they were to preach.
But that is not a command, it was something for them to do.