1、未初始化的channel读，阻塞
package main
import (
"fmt"
"time"
)
func main() {
var ch chan int
go check(ch)
fmt.Println("main runtime end")
time.Sleep(time.Second * 1000)
}
func check(ch chan int) {
select {
case i := <-ch:
fmt.Println("read ch data=", i)
}
fmt.Println("check runtime exit")
}
2、未初始化的channel写，阻塞
package main
import (
"fmt"
"time"
)
func main() {
go func() {
for {
time.Sleep(time.Second * 1)
}
}()
var ch chan int
go check(ch)
time.Sleep(time.Second * 1)
fmt.Println("xxxxxxx")
<-ch
fmt.Println("main runtime end")
time.Sleep(time.Second * 1000)
}
func check(ch chan int) {
defer func() {
if r := recover(); r != nil {
fmt.Println("recover ", r)
}
}()
ch <- 1
fmt.Println("check runtime exit")
}
3、向已关闭的channel读，返回默认值和false
package main
import (
"fmt"
"time"
)
func main() {
var ch chan int
ch = make(chan int)
go check(ch)
fmt.Println("main runtime end")
close(ch)
time.Sleep(time.Second * 1000)
}
func check(ch chan int) {
select {
case i, k := <-ch:
fmt.Println("read ch data=", i, " k=", k) //k=false i=0
}
fmt.Println("check runtime exit")
}
4、向已关闭的channel写，panic
package main
import (
"fmt"
"time"
)
func main() {
var ch chan int
ch = make(chan int)
close(ch)
ch <- 1
fmt.Println("end")
time.Sleep(time.Second * 1000)
}
5、time.Timer Stop后，time.Timer.C将阻塞
package main
import (
"fmt"
"time"
)
func main() {
tm := time.NewTimer(time.Second * 3)
go check(tm)
time.Sleep(time.Second * 1)
tm.Stop()
fmt.Println("main runtime end")
time.Sleep(time.Second * 1000)
}
func check(tm *time.Timer) {
select {
case i, k := <-tm.C: //阻塞
fmt.Println("read ch data=", i, " k=", k)
}
fmt.Println("check runtime exit")
}
6、无缓冲与有缓冲channel的重要区别，无缓冲的channel在写时必须有读携程，否则会阻塞。如下例子，超时后向exit发数据会阻塞，因为只有一个携程，此时没有其他携程对exit进行读。【踩了坑才理解深刻】
package main
import (
"fmt"
"time"
)
func main() {
exit := make(chan int)
go check(exit)
time.Sleep(time.Second * 100)
}
func check(exit chan int) {
tm := time.NewTimer(time.Second * 3)
select {
case <-exit:
fmt.Println("exit")
case <-tm.C:
fmt.Println("time out")
exit <- 1
fmt.Println("exit <- 1 ok")
}
fmt.Println("check runtime exit")
}
例子2：
package main
import (
"fmt"
"time"
)
func main() {
go func() {
for {
time.Sleep(time.Second * 1)
}
}()
exit := make(chan int, 1)
exit <- 1
fmt.Println("end")
}
这里会直接END，如果exit:=make(chan int),会阻塞在exit<-1
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