C4W stands for Check For Web.
https://forfuncsake.github.io/post/2017/08/trust-extra-ca-cert-in-go-app/
https://www.agwa.name/blog/post/parsing_tls_client_hello_with_cryptobyte
https://sematext.com/blog/ssl-certificate-error/
https://www.cossacklabs.com/blog/tls-validation-implementing-ocsp-and-crl-in-go/
https://github.com/the-gophers/go-action
https://cs.opensource.google/go/go/+/master:src/crypto/x509/root_linux.go