直接上代码：
1. 第一种情况， 如果没有select{}， main 主线程不会等待coroutine运行，导致coroutine得不到机会运行。
You are requesting eventual scheduling (using the two go statements)
of two goroutines and then you exit main without giving the scheduler
a chance to do anything.
有了select， 程序正常运行。
package main
import (
"fmt"
"time"
)
func main() {
go func1()
go func2()
select{}
}
func func1() {
for{
fmt.Println("here1")
time.Sleep(10 * time.Minute)
}
}
func func2() {
for{
fmt.Println("here2")
time.Sleep(10 * time.Minute)
}}
2. coroutine有机会运行，但是会发生死锁， fatal error: all goroutines are asleep - deadlock!
The goroutine executing func1 exited, ditto for func2. The main goroutine is blocked with no hope to recover while no other goroutine can be scheduled.
package main
import (
"fmt"
//"time"
)
func main() {
go func1()
go func2()
select {
}
}
func func1() {
fmt.Println("here1")
}
func func2() {
fmt.Println("here2")
}
3. 第三种情况， 正常运行。
package main
import (
"fmt"
)
var c = make(chan int, 2)
func main() {
go func1()
go func2()
<-c
<-c
fmt.Println("ok")
}
func func1() {
fmt.Println("here1")
c <- 1
}
func func2() {
fmt.Println("here2")
c <- 1
}
4. 实现上面的目的的另外一种方法：
var wg sync.WaitGroup
var urls = []string{
"http://www.golang.org/",
"http://www.google.com/",
"http://www.somestupidname.com/",
}
for _, url := range urls {
// Increment the WaitGroup counter.
wg.Add(1)
// Launch a goroutine to fetch the URL.
go func(url string) {
// Decrement the counter when the goroutine completes.
defer wg.Done()
// Fetch the URL.
http.Get(url)
}(url)
}
// Wait for all HTTP fetches to complete.
wg.Wait()有疑问加站长微信联系（非本文作者）
