Imports golang.org/x/sync/errgroup golang.org/x/crypto/acme knative.dev/pkg/apis golang.org/x/crypto/acme/autocert k8s.io/apimachinery/pkg/util/sets knative.dev/pkg/logging knative.dev/net-http01/pkg/challenger Standard library imports crypto/x509/pkix crypto/elliptic crypto/ecdsa context crypto/rand crypto/tls crypto/x509 errors fmt strings sync time