def key_file=(*args)
      path, passphrase = args.flatten
      ssl_context.key = OpenSSL::PKey::RSA.new(File.open(path), passphrase)
    end
def key_file=(*args)
      path, passphrase = args.flatten
      ssl_context.key = OpenSSL::PKey::RSA.new(File.open(path), passphrase)
    end
Set a path to a file containing a PEM-format client private key