verifiable credential example

[andorsk]

please merge #126 first then this will follow:

➜  vc git:(vc-example) go run vc.go
Created Verifiable Credential:
 {
  "@context": [
    "https://www.w3.org/2018/credentials/v1",
    "https://www.w3.org/2018/credentials/examples/v1"
  ],
  "id": "http://example.edu/credentials/1872",
  "type": [
    "VerifiableCredential",
    "AlumniCredential"
  ],
  "issuer": "https://example.edu/issuers/565049",
  "issuanceDate": "2010-01-01T19:23:24Z",
  "credentialSubject": {
    "alumniOf": {
      "id": "did:example:c276e12ec21ebfeb1f712ebc6f1",
      "name": [
        {
          "lang": "en",
          "value": "Example University"
        },
        {
          "lang": "fr",
          "value": "Exemple d'Université"
        }
      ]
    },
    "id": "did:example:ebfeb1f712ebc6f1c276e12ec21"
  }```

[decentralgabe]

@andorsk
before moving your examples, let's agree on whether they should be tests or as is.

the main benefit of tests:

• not included in the binary when you're using the sdk as a dependency
• simple to run independently
• can easily determine if the examples break, as tests are run for a CI-precondition
• simpler error handling with assertions

benefits of main.go:

• easier to see "real world" usage

what do you think?

[andorsk]

Me personally, I've suggested we follow precedence and standards, which is that these are not tests (b/c they aren't) and run as example files. There are more reasons I can give, but ultimately I don't think we are facing a unique problem here. It seems to me, how things have been done historically seems like a reasonable way to handle it.

See here for some examples of examples 😆 :
https://github.com/golang-standards/project-layout/tree/master/examples
https://github.com/cossacklabs/themis/tree/master/docs/examples/go

That being said: I'd suggest three lines here of action, which would result in a conclusion:

1. We can agree based upon the evidence above. But given we've both highlighted reasons and have not changed positions, it seems like it's at an impasse right now.
2. We can ask some third person to weigh in and tie break this.
3. If you feel strongly about this, I can change them to tests. As I mentioned before, It's more important we have something in for now. There are things I'm going to want to dig my heel in potentially later, but this isn't one of them and I'm willing to budge on this if that's going to move things forward.

What's the most important here is we have some examples available for everyone else. We can always change things later if we realize we made a mistake here.

[decentralgabe]

@andorsk I appreciate the links, I wasn't aware this was a convention.

I'm OK to merge as-is. In the future, we can consider creating a new repo ssi-sdk-examples and moving them there; however for now this is an excellent start.

I noticed other examples rely on handleError, perhaps worth creating an examples util file or something similar.

[andorsk]

Thanks @decentralgabe for merging this in.

And yep! I think that's totally fair. In fact, maybe we should see about putting all the examples in the same directory. Rather than different ones.

Lots of work to do on the examples! I'm happy to chat about scope for improving them.