Unpredictable behavior in concurrent message handling

package main

import (
	"fmt"
	"time"
)

func handleMessages(ch1, ch2 chan string) {
	for {
		select {
		case msg1 := <-ch1:
			fmt.Println("Received from ch1:", msg1)
		case msg2 := <-ch2:
			fmt.Println("Received from ch2:", msg2)
		}
	}
}

func main() {
	ch1 := make(chan string)
	ch2 := make(chan string)

	go func() {
		for i := 0; i < 5; i++ {
			ch1 <- fmt.Sprintf("Message %d from ch1", i)
			time.Sleep(10 * time.Millisecond)
		}
		close(ch1)
	}()

	go func() {
		for i := 0; i < 5; i++ {
			ch2 <- fmt.Sprintf("Message %d from ch2", i)
			time.Sleep(10 * time.Millisecond)
		}
		close(ch2)
	}()

	handleMessages(ch1, ch2)
}