如何在不阻塞的情况下判断 Goroutine 是否完成？

package main

import (
    "fmt"
    "time"
)

func worker(ch chan int) {
    defer close(ch) // Goroutine 完成后关闭 channel
    time.Sleep(2 * time.Second)
    ch <- 123 // 向 channel 发送数据
}

func main() {
    ch := make(chan int)
    go worker(ch)

    // 非阻塞地检查 Goroutine 是否完成
    for {
        select {
        case val, ok := <-ch:
            if ok {
                fmt.Println("Received:", val)
                fmt.Println("Goroutine is still running.")
            } else {
                fmt.Println("Channel is closed.")
                fmt.Println("Goroutine has finished.")
                return
            }
        default:
            fmt.Println("No data available yet, checking again...")
            time.Sleep(500 * time.Millisecond) // 避免 CPU 占用过高
        }
    }
}