int变量输出未出现在另一个包中

// 包A
package packageA

var X int = 10

// 包B
package packageB

import "packageA"

func main() {
    fmt.Println(packageA.X)
}

// 包A
package packageA

func GetX() int {
    return 10
}

// 包B
package packageB

import "packageA"

func main() {
    x := packageA.GetX()
    fmt.Println(x)
}

// 包A
package packageA

type MyStruct struct {
    X int
}

// 包B
package packageB

import "packageA"

func main() {
    myStruct := packageA.MyStruct{X: 10}
    fmt.Println(myStruct.X)
}