v2.0.0-beta.5

Changelog

3c3be56 build: bump language version to Go 1.17
6cac235 chore(ci): bump golangci-lint to 1.42
40da914 ci: bump Go version to 1.17
2720dad ci: enable errname linter
4422f5f feat: add OptSignWithTime
6535cd5 fix: ErrNoObjects from GetDescriptor(s)
26cff39 fix: replace usage of deprecated ioutil package
ed685b2 refactor: pass concrete type to VerifyCallback
b842110 refactor: use struct to accumulate sign options
665eac1 refactor: use struct to accumulate verify options
62860b7 style: add new build constraint format messages