为什么按通道接收值时看不到输出

Question

in the next example, I don't understand why end value not printed when received

package main

import "fmt"

func main() {
    start := make(chan int)
    end := make(chan int)

    go func() {
        fmt.Println("Start")
        fmt.Println(<-start)
    }()

    go func() {
        fmt.Println("End")
        fmt.Println(<-end)
    }()

    start <- 1
    end <- 2
}

I know sync.WaitGroup can solve this problem.

Answer 1

Because the program exits when it reaches the end of func main, regardless of whether any other goroutines are running. As soon as the second function receives from the end channel, main's send on that channel is unblocked and the program finishes, before the received value gets a chance to be passed to Println.