Update FlexValue type

[sugyan]

Fix #124.

this is breaking change

For enable to pass 0 as value, changed the type of flex field from int to FlexValueType (equals to *int), so developers need to change values to FlexValueType. So I added a helper function FlexInt() to create FlexValueType value.

[k2wanko]

I think that the function name better be FlexInt.

[sugyan]

Thanks, I renamed it.

[k2wanko]

I gave a little comment. 👀

[sugyan]

Fixed tests 🙇

[linxGnu]

@sugyan Could you please describe why we should have this?

Referencing type FlexValueType *int could cause data race in user's application. It's better to make it immutable like before.

My suggestion is just letting:

type FlexValueType = int // alias type

And no need:

func FlexInt(...)

[k2wanko]

@linxGnu Good suggestion.
In adopting this method, it seems necessary to end support of less than 1.9.

https://github.com/line/line-bot-sdk-go/blob/bc678e0b74717c1daf0836e13bbed9dd3e6988b8/README.md#requirements

[linxGnu]

@k2wanko I think so. I believe user has upgrade to go 1.9 for huge improvement at GC and runtime. So I do not think we need to support go1.7 and 1.8.

[sugyan]

@linxGnu Thanks for your reviewing and comments.
I updated my branch, but your proposal was not such a change?
If you know a better solution for #124, I'd be happy if you give another pull-request.

[linxGnu]

@sugyan I think you may misunderstand my comment.

type FlexValueType *int

You should not do that. Because you are making reference to an int outside. I think in our case, FlexValueType should be immutable. So it should be like this:

type FlexValueType = int

Yes, it does not change anything!
But we still archive the goal of making code/type clearer.

[sugyan]

I updated my branch again. How about this?

[k2wanko]

FlexInt is not necessary when using type alias.

[sugyan]

hmm.., how pass 0 as value?
https://github.com/line/line-bot-sdk-go/pull/129/files#diff-40bd644208f7397ac51144bbe03b721bR387

[linxGnu]

I think *FlexValueType is not necessary. I wonder why we have to embedded the * (reference) instead of value 🤔

[sugyan]

Did you read #124 ?
flex is an optional field and tagged as omitempty, but it should accept the value 0 as not the default value.
So I thought that we have to embed the * (reference) instead of value to omit this field only if the reference is null.

[linxGnu]

👍 @sugyan Sound reasonable to me. Thank you very much for explanation.

I'm sorry. It is necessary for assembling the structure.

[linxGnu]

LGTM

[mokejp]

It looks good in this case.
However, I am concerned that similar types will increase if optional fields increase in the future.

I think that using *int and adding func Int(v int) *int helper function is the simple and versatile way.

[sugyan]

Thanks for your comment.
I removed alias type and renamed the helper function to IntPtr.

[mokejp]

LGTM! Thanks.