SSL certificate challenges

I have a .pem file that contains a private and a public key.

I need help in order to extract the certificate and to send the request using httpoison.

Below is how I am currently doing it in Ruby and sending the request through Faraday gem.

SSL_OPTS={client_cert: OpenSSL::X509::Certificate.new(File.read(pem_file)), client_key: OpenSSL::PKey::RSA.new(File.read(pem_file), 'testpem15')}

conn=Faraday.new(:url => "https://ip:port", :ssl=>SSL_OPTS,
    :headers => HEADER) do |faraday|
    faraday.response :logger                  
    faraday.adapter  Faraday.default_adapter  
end

I am, however, rewriting the application in Elixir.

Any help will be most appreciated.

Thanks.

Jerry