VIDEO: What Church Manual Dates from the Time of the Apostles?

I don’t know if I’m correct in this, but I have been told that the Didache was written somewhere between AD 50 and AD 120. In other words, around the same time as the New Testament.
I also wonder if the term ‘Apostle’ in the Didache would include other people than just the twelve. In the same way that Barnabas or Timothy might be called ‘Apostles.’