Add go package as a submodule

[w4ll3]

This adds a sub module to DIDKit didkit-go. The reason it is being added this way is to make it possible to be used as a module in a Go program. Once this is merged the instructions at didkit-go, which are simpler, will work.

Testing at DIDKit

• Checkout to this branch
• Init the submodule

git submodule update --init

• Make sure to have the C target built

make -C extern/didkit/lib ../target/test/c.stamp

• Run the tests

cd lib/didkit-go
go test

How to test it on a Go program

• Create a Go program
• Init git in the repo

git init

• Add DIDKit and SSI as submodules to your repo. (Since this is not merged yet you have to manually init the sub modules)

go get github.com/spruceid/didkit-go
git submodule add https://github.com/spruceid/didkit.git extern/didkit
git submodule add https://github.com/spruceid/ssi.git extern/ssi
cd extern/didkit
git checkout feature/go-package
git submodule update --init
cd ../ssi
git submodule update --init
cd ../..

• Build DIDKit C target

make -C extern/didkit/lib ../target/test/c.stamp

• Update the lib target

go mod edit -replace=github.com/spruceid/didkit-go=./extern/didkit/lib/didkit-go

• Write some code to test the lib

package main

import (
        "fmt"

        "github.com/spruceid/didkit-go"
)

func main() {
        fmt.Println(didkit.GenerateEd25519Key())
}

Testing example application

• Checkout to this branch
• Init the submodule

git submodule update --init

• Follow the instructions in the example README

[clehner]

Nice! Go tests passed. Example program builds and runs. For the example program, instead of using submodules for ssi and didkit, I used symlinks to my existing copies of them.

Other ideas:

• If users of the didkit go package must have a local copy of ssi and/or didkit (as submodules or otherwise), could it be useful to have an example repo demonstrating this usage?
• For the other didkit FFI libraries we usually have tests in GitHub actions. If not adding them here, should an issue be opened for this?
• The other didkit interfaces are in this repo directly, while this one uses a separate repo which is included as a submodule. Could it have been included directly? I assume it did not work to do so, but wonder why.

[w4ll3]

• If users of the didkit go package must have a local copy of ssi and/or didkit (as submodules or otherwise), could it be useful to have an example repo demonstrating this usage?

• You mean like a Hello World project for didkit-go?

• The other didkit interfaces are in this repo directly, while this one uses a separate repo which is included as a submodule. Could it have been included directly? I assume it did not work to do so, but wonder why.

• It seems that go packages must be at the root of the repo, that's why it's added as a sub module

[clehner]

CI was added; thanks @w4ll3. Tests still pass after merging in changes from main (2eb854d). The submodule didkit-go repo looks good to me.

I tried using the example more, and was able to get a verifiable credential, but was not able to present it. Also, I don't know if it makes sense to use a DID as the verifiable credential id. Usually a DID is an id of a DID document, and a verifiable credential is not a DID document. In this case the keypair associated with the DID used in the VC id is not stored, so it does not appear to serve a useful purpose (e.g. for signing/verification). A UUID could be used instead - or the id property could be removed if the app doesn't need to store/retrieve the credentials by id. For the sake of enabling didkit-go, I think this PR could be merged as-is and new issues created to track these things.

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