If thou count me therefore a partner; if thou holdest me for a friend—by our friendship entreat this. The strongest form of entreaty possible to be used. κοινωνία in Acts 2:42 refers to the Holy Communion, and in 1 Corinthians 10:16-21 partakers of it are plainly called by implication κοινωνοὶ—partakers, or, as we should say, "communicants."
But here the sense is apparently as above; literally, a partner.