func selectFromChannels() {
	ch1 := make(chan float64)
	ch2 := make(chan float64)

	go func() {
		ch1 <- math.Pi
		close(ch1)
	}()
	go func() {
		ch2 <- math.E
		close(ch2)
	}()

	select {
	case v := <-ch1:
		fmt.Printf("Received from ch1: %.5f\n", v)
	case v := <-ch2:
		fmt.Printf("Received from ch2: %.5f\n", v)
	}
}