fix(*): validate stateExecTimeout iso8601

[lsytj0413]

Signed-off-by: lsytj0413 511121939@qq.com

Many thanks for submitting your Pull Request ❤️!

What this PR does / why we need it:

• add validator for sleep state field
• refactor StateExecTimeout unmarshal function

Special notes for reviewers:

Additional information (if needed):

[ricardozanini]

@lsytj0413 see here: https://github.com/lsytj0413/swf-sdk-go/pull/1

I'm still failing to understand when the recursion occurs.

[lsytj0413]

lsytj0413#1

unmarshalJSON1 is previous version implement, and i think unmarshalJSON2（secondary version implement) is more concise:

1. it only call Unmarshal once, the previous version implement may call Unmarshal 2/3 times
2. it independent of the field number in struct, the previous version implement may call unmarshal for every field.（take a look at OAuth2AuthProperties.UnmarshalJson，it have a huge number of unmarshalKey）

[lsytj0413]

I'm still failing to understand when the recursion occurs.

the recursion occurs when:

1. timeout is an object, and we use unmarshalJSON2 implement
2. first byts is '{', we detect data is object, and call json.Unmarshal(data, s)
3. because object s（it's type is *StateExecTimeout） implement json.Unmarshaler interface, so the unmarshalJSON2 recursion called by json.Unmarshal function
4. go to step 2

so we must use another type which didn't implement json.Unmarshaler interface for step 2.

[ricardozanini]

send me a workflow to include in the unit test, please.

[lsytj0413]

send me a workflow to include in the unit test, please.

I have change PR to secondary implement with all unit test.
PTAL

[ricardozanini]

Looking good!