It would be better if defaults are set before hand at the time of initialization of window

the default value is being set in the implementation under method getFieldValues. if we move the default value into the constructor, then that constructor has to deal with two different default values, one for version 1 and another is for version 2. I believe the current constructor shouldn't handle such a thing.

however, if we really want to specify the default value during construction, we can create unexported constructors for window version 1 (and version 2 as well, if required). each of them will handle the default value for each one. meaning, the current constructor do not need to deal with it. for example:

NewWindow() {
  if version == 1 {
    newWindowV1()
  } else {
    newWindowV2()
}

// each constructor will specify default value

why we need this check? and these intermediate variables we can directly refer to the window variables

this is to avoid panic. for example, the spec being used does not have Window field being configured, meaning it's nil. if we do not check it first and access the field Window, panic will hapen

this should be handled within the constructor

this is in case the job spec version is not specified. it's like a default value. the constructor's responsibility is construct a window based on valid inputs, or return error otherwise. if there's any invalid input such as version, I believe the constructor shouldn't assume the version of a spec. if there's a strong reason to do otherwise, then we need to at least change the function name to be not NewWindow