Composing with channels

channel_play.jl

# sum worker
function sum_worker(source)
    target = Channel()
    task = @async while true
        args = take!(source)
        args === nothing && break
        result = sum(args)
        push!(target, result)
    end
    return (output = target, task = task)
end

# Fan-out.  Take 1 msg from channel and distribute to N other channels.
function fanout(source; n = 1)
    targets = [Channel() for i in 1:n]
    task = @async while true
        msg = take!(source)
        args === nothing && break
        foreach(target -> push!(target, msg), targets)
    end
    return (output = targets, task = task)
end

source = Channel()
harness = sum_worker(source)  # this is async
while true   # test worker
    println(take!(harness.output))
end