How to generate key.pem, cert.pem certificates from pfx or pem?

Question

go

there is such code in golang and pfx and PEM certificates. I made pem from pfx. Wrote a request in PHP and the request passed.

cert, err := tls.LoadX509KeyPair("testdata/example-cert.pem", "testdata/example-key.pem")

  defaultTransport := http.DefaultTransport.(*http.Transport)

  tr := &http.Transport{
    Proxy:                 defaultTransport.Proxy,
    DialContext:           defaultTransport.DialContext,
    MaxIdleConns:          100,
    IdleConnTimeout:       30 * time.Second,
    ExpectContinueTimeout: defaultTransport.ExpectContinueTimeout,
    TLSHandshakeTimeout:   defaultTransport.TLSHandshakeTimeout,
    TLSClientConfig: &tls.Config{
      InsecureSkipVerify: true,
      Certificates:       []tls.Certificate{cert},
      //RootCAs:            caCertPool,
    },
  }

how to generate them correctly? or maybe the code is wrong

. The request must be to a third-party service (which gave the certificate) but does not pass SSL verification.