Optional field with json tag "omitempty" should be type of pointer.

[nvthongswansea]

Optional field with json tag "omitempty" should be type of pointer, since the optional fields usually accepts 3 types of input: nil (omitted when the field is nil), empty (Should not be omitted. eg: "" for string, 0 for int), and not empty. E.g:
Labels []string json:"labels,omitempty"

should be

Labels *[]string json:"labels,omitempty"