Go语言之如何给*int32类型赋值

直接上代码:

package main

import "fmt"

func main() {
    var num *int32
    var i int32 = 5
    // 针对*int32的，先创建一个i类型，然后取i的地址，赋值给*int32
    num = &i
    fmt.Println("=====>:\t", num)
    fmt.Println("=====>:\t", *num)
}

运行结果：

=====>:  0xc042064080
=====>:  5

Process finished with exit code 0

下面的形式是不可以的：

package main

import "fmt"

func main() {
    var num *int32
    *num = 5
    fmt.Println("=====>:\t", num)
    fmt.Println("=====>:\t", *num)
}

运行结果：

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x1 addr=0x0 pc=0x48b4ea]

goroutine 1 [running]:
main.main()
    E:/Program/go2/goPath/src/xingej-go/xingej-go/xingej-go666/string/test.go:7 +0x2a

Process finished with exit code 2  

原因？
  可能是取不到常量5的地址