Unable to create online web-page - go

Question

I am trying to create Golang web-pages...
Progress:
Ubuntu 18.04 installed both locally and on a Linode VPS.
Created and compiled a local Golang "Hello World" script that renders OK both locally and online.
Created a net/http Golang script that works OK when called locally http://localhost:8080/testing to see if it works
Uploaded the script to the Linode server and initial status messages appear but when calling http:123.456.789.32:8080/testing to see if it works the browser freezes.
//
// Golang - main.go
//
package main
import (
"net/http"
)
func sayHello(w http.ResponseWriter, r *http.Request) {
message := r.URL.Path
message = "Hello " + message
w.Write([]byte(message))
}
func main() {
http.HandleFunc("/", sayHello)
if err := http.ListenAndServe(":8080", nil); err != nil {
panic(err)
}
}
There are no errors or warnings rendered and unable to find any log references.
Can error and warnings similar to PHP error_reporting(-1), declare(strict_types=1) etc be logged or rendered?

Answer 1

A quick check with Nmap showed this result:
nmap -sV -p 8080 <yourIP>
Starting Nmap 7.70 ( https://nmap.org ) at 2019-07-04 07:45 CEST
Nmap scan report for <your-domain>.com (<yourIP>)
Host is up (0.032s latency).
PORT STATE SERVICE VERSION
8080/tcp filtered http-proxy
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 0.90 seconds
The state of "filtered" actually means that there was no response on that port as opposed to an outright rejection of the request.
Check the output of iptables -L -n. Presumably, you have a firewall running and blocking port 8080. Do not simply deactivate the firewall, but read up on how to open port 8080 in the firewall product you are using. Linode has guides for the commonly used/preinstalled firewalls of various Linux distributions.
If you plan to go into production, please have someone help you to ensure security and availability of your deployment.