When next goroutine is executed?

Question

I am looking at the example from https://blog.golang.org/pipelines:

func main() {
    in := gen(2, 3)

    // Distribute the sq work across two goroutines that both read from in.
    c1 := sq(in)

    // When does this line below execute and what is in `in`?
    c2 := sq(in)

    // Consume the merged output from c1 and c2.
    for n := range merge(c1, c2) {
        fmt.Println(n) // 4 then 9, or 9 then 4
    }
}

When does c2 := sq(in) run? As what I understand, it executes not when previous line finishes, but instantly as that is a goroutine.

Will c2 receive the next incoming message that is after coming after the message that is received by c1?

Answer 1

Your code does not use goroutines, in order to use go routines you should do something like this:

q := make(chan type) 
go sq(in, q)
go sq(in, q)

for elem := range q {
    fmt.Println(elem)
}

and sq must return the value through a channel

func sq(in type, q chan type) {
     ...
     q <- valueFromIn
     ...
}

Also you can use WaitGroup to wait for goroutines to finish.