update go deps in examples/go.mod

[dmitris]

Summary

Update Go dependencies to be able to run go install -v github.com/sigstore/sigstore-go/examples/oci-image-verification in the examples/ directory. Currently when trying to run that command, I'm getting an error:

$ GOBIN=/tmp/bin go install -v github.com/sigstore/sigstore-go/examples/oci-image-verification
no required module provides package github.com/sigstore/sigstore-go/examples/oci-image-verification; to add it:
	go get github.com/sigstore/sigstore-go/examples/oci-image-verification

This may partially overlap with the open #410 - if you merge that one first, I'll rebase on trunk.

Release Note

NONE

Documentation

n/a

[codysoyland]

Hi @dmitris, thanks for the PR. We intentionally keep the oci-image-verification module separate from the main module to reduce dependencies in the main module. Can you use make build-examples or go install -C ./examples/oci-image-verification . instead?

[dmitris]

Can you use make build-examples or go install -C ./examples/oci-image-verification . instead?

Sure - would be good to highlight that in the README for examples/ - opened #412 for that.