TLS error with HTTPS calls via proxy in Go - go

Question

I want to make https calls via a third party proxy using Go.
The third party proxy accepts a username and password.
My code works fine when I call the proxy using http. But I get a runtime error when I change the proxy to https.
The error message is:
proxyconnect tcp: tls: first record does not look like a TLS handshake
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x1248521]
package main
import (
"log"
"net/http"
"net/url"
)
func main() {
// proxyURL - change to https get runtime error
proxyStr := "http://username:password#ip:port"
proxyURL, err := url.Parse(proxyStr)
if err != nil { log.Println(err) }
// targetURL
targetStr := "https://httpbin.org/get"
targetURL, err := url.Parse(targetStr)
if err != nil { log.Println(err) }
//config Transport w Proxy
transport := &http.Transport{
Proxy: http.ProxyURL(proxyURL),
}
//config Client w Transport
client := &http.Client{
Transport: transport,
}
//config Request
request, err := http.NewRequest("GET", targetURL.String(), nil)
if err != nil { log.Println(err) }
log.Println("Requesting", targetStr)
//try it
response, err := client.Do(request)
if err != nil { log.Println(err) }
log.Println(response.Status)
}