So that we can advertise a slightly more expansive default set of
signature/hash algorithms in the signature_algorithms extension of
the TLS Client Hello, provide an option to use a pre-defined override.
This also splits up the TLS connection helper in tls.go, so that the
tls.Config can be modified by a scanner module.
This pins dependencies via go mod init. Regular builds should still
work, so this won't affect CI. It overrides the default set of deps for
ZFlags, to point to v1.4.0-beta.1. This gets the ParseCommandLine
function.
