Run with

go run *.go

  "UnsetUserArray": null,
  "UnsetIntArray": null,

contrast the output with

. environment; go run *.go

  "UnsetUserArray": [
    "tom",
    "dick",
    "harry"
  ],
  "UnsetIntArray": [
    9,
    8,
    0,
    5,
    4,
    3,
    2,
    1
  ],