go for range坑和闭包坑的分析

看程序：

package main
import (
  "fmt"
  "time"
)
func main() {
  str := []string{"I","like","Golang"}
  for _, v := range str{
   v += "good"
  }
  for k, v := range str{
   fmt.Println(k, v)
  }
  time.Sleep(1e9)
}

结果：

0 I
1 like
2 Golang

想一想，为什么。

再看：

package main
import (
  "fmt"
  "time"
)
func main() {
  str := []string{"I","like","Golang"}
  for k, v := range str{
   fmt.Println(&k, &v)
  }
  time.Sleep(1e9)
}

结果：

0xc000012050 0xc00000e1e0
0xc000012050 0xc00000e1e0
0xc000012050 0xc00000e1e0

想一想，为什么。

再看：

package main
import (
  "fmt"
  "time"
)
func main() {
  str := []string{"I","like","Golang"}
  for k, v := range str{
   str = append(str, "good")
   fmt.Println(k, v)
  }
  time.Sleep(1e9)
}

结果：

0 I
1 like
2 Golang

想一想，为什么。

再看：

package main
import (
  "fmt"
  "time"
)
func main() {
  str := []string{"I","like","Golang"}
  for k, v := range str{
   go func(i int, s string){
    fmt.Println(i, s, k, v)
   }(k, v)
  }
  time.Sleep(1e9)
}

结果：

0 I 2 Golang
1 like 2 Golang
2 Golang 2 Golang

想一想，为什么。

最后再看：

package main
import (
  "fmt"
  "time"
)
func main() {
  str := []string{"I","like","Golang"}
  for k, v := range str{
   go func(i int, s string){
    fmt.Println(i, s, k, v)
   }(k, v)
   time.Sleep(1e9)
  }
  time.Sleep(5e9)
}

结果：