How to send a https request with a certificate golang

You need to add CA of your certificate to your transport like:

package main

import (
    "crypto/tls"
    "io/ioutil"
    "log"
    "net/http"
    "crypto/x509"
)

func main() {
    caCert, err := ioutil.ReadFile("rootCA.crt")
    if err != nil {
        log.Fatal(err)
    }
    caCertPool := x509.NewCertPool()
    caCertPool.AppendCertsFromPEM(caCert)

    client := &http.Client{
        Transport: &http.Transport{
            TLSClientConfig: &tls.Config{
                RootCAs:      caCertPool,
            },
        },
    }

    _, err := client.Get("https://secure.domain.com")
    if err != nil {
        panic(err)
    }
}

But I guess you just haven't created CA to make your certificates. Here is the list of commands without explanation which can help you to make certificates signed with your own CA. For more information, you can Google it.

1. Generating CA

   openssl genrsa -out rootCA.key 4096
   openssl req -x509 -new -key rootCA.key -days 3650 -out rootCA.crt
   

2. Generate certificate for secure.domain.com signed with created CA

   openssl genrsa -out secure.domain.com.key 2048
   openssl req -new -key secure.domain.com.key -out secure.domain.com.csr
   #In answer to question `Common Name (e.g. server FQDN or YOUR name) []:` you should set `secure.domain.com` (your real domain name)
   openssl x509 -req -in secure.domain.com.csr -CA rootCA.crt -CAkey rootCA.key -CAcreateserial -days 365 -out secure.domain.com.crt