What does `(<-chan Delivery)(deliveries)` do?

Question

I found this line:

return (<-chan Delivery)(deliveries), nil

https://github.com/streadway/amqp/blob/master/channel.go#L1089

What does it do? Why the double parentheses?

Answer 1

It's a type conversion. In your case, it converts chan Delivery (two-way channel of Delivery values) to <-chan Delivery (receive-only channel of Delivery values).

Answer 2

It is a type conversion. Returns deliveries as a read-only channel.