gochanneldeadlock
chan
package main

import (
  "fmt"
)

func main() {
  ch := make(chan int, 3)
  <-ch
}

输出结果：

fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan receive]:
main.main()
  /home/work/code/golang/src/interview/go/deadlock/test.go:9 +0x56

Process finished with exit code 2

解决方式：

select case default
package main

import (
  "fmt"
)

func main() {
  ch := make(chan int, 3)

  select {
  case v := <-ch:
    fmt.Println(v)
  default:
    fmt.Println("chan no data")
  }
}
channel
package main

import "fmt"

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

  ch <- 1 // 无缓冲在此写入数据，却没有读数据，阻塞住

  fmt.Println(<-ch) // 被上面阻塞，无法被执行到
}

输出结果：

fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan send]:
main.main()
  /home/work/code/golang/src/interview/go/deadlock/test02.go:8 +0x59

Process finished with exit code 2

解决方式：

chan
package main

import "fmt"

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

  go func() {
    ch <- 1 // 开启子goroutine写入数据
  }()

  fmt.Println(<-ch) // 阻塞住，一旦ch有数据，则读取成功
}
chan
package main

import "fmt"

func main() {
  ch := make(chan int, 1)

  ch <- 1

  fmt.Println(<-ch)
}
chan
package main

import (
  "fmt"
)

func main() {
  ch := make(chan int, 3)
  ch <- 1
  ch <- 2
  ch <- 3
  ch <- 4 // 超过最大容量，阻塞main协程，产生deadlock

  for v := range ch {
    fmt.Println(v)
  }
}

解决方式：
a. 增加缓冲容量，保证能满足写入所有数据；

select case defaultdemo
for range
package main

import (
  "fmt"
)

func main() {
  ch := make(chan int, 3)

  ch <- 1
  ch <- 2
  ch <- 3

  // range 一直读取直到chan关闭，否则产生阻塞死锁
  for v := range ch {
    fmt.Println(v)
  }
}

输出结果：

1
2
3
fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan receive]:
main.main()
  /home/work/code/golang/src/interview/go/deadlock/test04.go:15 +0x115

Process finished with exit code 2

解决方式：

channel
sleep
package main

import (
  "fmt"
  "time"
)

func main() {
  ch := make(chan int, 3)

  ch <- 1
  ch <- 2
  ch <- 3

  close(ch) // 解决方式1：关闭chan

  // range 一直读取直到chan关闭，否则产生阻塞死锁
  // 解决方式2：开启子协程，主协程sleep等待
  go func() {
    for v := range ch {
      fmt.Println(v)
    }
  }()

  time.Sleep(1e9)
}

【小结】

channelbuffered channelunbuffered channeldeadlock