The macro is just a wrapper around this (and a couple of other functions): https://docs.rs/futures/0.3.0/futures/future/fn.join.html https://docs.rs/futures/0.3

The macro is just a wrapper around this (and a couple of other functions): https://docs.rs/futures/0.3.0/futures/future/fn.join.html https://docs.rs/futures/0.3.0/futures/future/fn.join.html And from a quick scan of the source it doesn't look like anything there is impossible to implement in userspace: https://docs.rs/futures-util/0.3.0/src/futures_util/future/join.rs.html#11-118 https://docs.rs/futures-util/0.3.0/src/futures_util/future/j...