mix.go

package mix

func Mix(high <-chan interface{}, low <-chan interface{}) <-chan interface{} {
	c := make(chan interface{})
	go func() {
		defer close(c)
		var vh, vl interface{}
		highOpen := true
		lowOpen := true
		var ok bool
		for highOpen || lowOpen {
			select {
			case vh, ok = <-high:
				if !ok {
					highOpen = false
					high = nil
					break
				}
				c <- vh
				continue
			case vl, ok = <-low:
				if !ok {
					lowOpen = false
					low = nil
					break
				}
lowloop:
				for {
					select {
					case c <- vl:
						break lowloop
					case vh, ok = <-high:
						if !ok {
							highOpen = false
							high = nil
							c <- vl
							break lowloop
						}
						c <- vh
						continue
					}
				}
			}
		}
	}()
	return c
}

t_test.go

package mix

import (
	"testing"
	"time"
)

func TestDoubleChan(t *testing.T) {
	c1 := make(chan interface{})
	c2 := make(chan interface{})
	doubleChan := Mix(c1, c2)

	go func() {
		time.Sleep(time.Millisecond * 50)
		for i := 0; i < 3; i++ {
			c1 <- "one"
			time.Sleep(time.Millisecond * 50)
		}
	}()

	go func() {
		for i := 0; i < 3; i++ {
			c2 <- "two"
			time.Sleep(time.Millisecond * 50)
		}
	}()

	expects := []string{"two", "one", "one", "one", "two", "two"}

	for _, expect := range expects {
		msg := <-doubleChan
		t.Log(msg)
		if msg != expect {
			t.Error("Expect:", expect)
		}
		time.Sleep(time.Millisecond * 200)
	}
}