go - Why can't I append to a slice that's the property of a struct in golang?

Question

I'm trying to append a value to a golang slice, the code works if it's called in the first method, but if this method calls another method, the code seems to fail.

Examples (Test3 is what I was originally trying to do):

package main

import (
  "fmt"
)

// This works

type Test1 struct {
  all []int
}

func (c Test1) run() []int {
  for i := 0; i < 2; i++ {
    c.all = append(c.all, i)
  }
  return c.all
}

// This works

var gloabl_all []int

type Test2 struct {}

func (c Test2) run() []int {
  c.combo()
  return gloabl_all
}

func (c Test2) combo() {
  for i := 0; i < 2; i++ {
    gloabl_all = append(gloabl_all, i)
  }
}

// This doesn't

type Test3 struct {
  all []int
}

func (c Test3) run() []int {
  c.combo()
  return c.all
}

func (c Test3) combo() {
  for i := 0; i < 2; i++ {
    c.all = append(c.all, i)
    fmt.Println("Test3 step", i + 1, c.all)
  }
}

func main() {
  test1 := &Test1{}
  fmt.Println("Test1 final:", test1.run(), "
")

  test2 := &Test2{}
  fmt.Println("Test2 final:", test2.run(), "
")

  test3 := &Test3{}
  fmt.Println("Test3 final:", test3.run())
}

This outputs:

Test1 final: [0 1] 

Test2 final: [0 1] 

Test3 step 1 [0]
Test3 step 2 [0 1]
Test3 final: []

Playground copy: https://play.golang.org/p/upEXINUvNu

Any help would be greatly appreciated!

Answer 1

Waitting for answers