Go: What is the pipeline pattern in Go?

1// Generator: creates data
2func generate(nums ...int) <-chan int {
3    out := make(chan int)
4    go func() {
5        defer close(out)
6        for _, n := range nums {
7            out <- n
8        }
9    }()
10    return out
11}
12
13// Worker: processes data
14func square(in <-chan int) <-chan int {
15    out := make(chan int)
16    go func() {
17        defer close(out)
18        for n := range in {
19            out <- n * n
20        }
21    }()
22    return out
23}
24
25func filter(in <-chan int, pred func(int) bool) <-chan int {
26    out := make(chan int)
27    go func() {
28        defer close(out)
29        for n := range in {
30            if pred(n) {
31                out <- n
32            }
33        }
34    }()
35    return out
36}
37
38// Usage
39ch := generate(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
40squared := square(ch)
41evens := filter(squared, func(n int) bool { return n%2 == 0 })
42
43for n := range evens {
44    fmt.Println(n)  // 4, 16, 36, 64, 100
45}
46
47// With done-channel for cancellation
48func genDone(done <-chan struct{}, nums ...int) <-chan int {
49    out := make(chan int)
50    go func() {
51        defer close(out)
52        for _, n := range nums {
53            select {
54            case out <- n:
55            case <-done:
56                return
57            }
58        }
59    }()
60    return out
61}