main.go

package main

import (
   "net/http"
   "fmt"
   "time"
   "html/template"
)

//Create a struct that holds information to be displayed in our HTML file
type Welcome struct {
   Name string
   Time string
}

//Go application entrypoint
func main() {
tick := time.NewTicker(500 * time.Millisecond)
   //Instantiate a Welcome struct object and pass in some random information. 
   //We shall get the name of the user as a query parameter from the URL
   welcome := Welcome{"Anonymous", time.Now().Format(time.Stamp)}
   //We tell Go exactly where we can find our html file. We ask Go to parse the html file (Notice
   // the relative path). We wrap it in a call to template.Must() which handles any errors and halts if there are fatal errors
   
   templates := template.Must(template.ParseFiles("templates/welcome-template.html"))

   //Our HTML comes with CSS that go needs to provide when we run the app. Here we tell go to create
   // a handle that looks in the static directory, go then uses the "/static/" as a url that our
   //html can refer to when looking for our css and other files. 
   go func() {
        for range tick.C {
            welcome.Time = time.Now().Format(time.Stamp);
        }
    }()
   http.Handle("/static/", //final url can be anything
      http.StripPrefix("/static/",
         http.FileServer(http.Dir("static")))) //Go looks in the relative "static" directory first using http.FileServer(), then matches it to a
         //url of our choice as shown in http.Handle("/static/"). This url is what we need when referencing our css files
         //once the server begins. Our html code would therefore be <link rel="stylesheet"  href="/static/stylesheet/...">
         //It is important to note the url in http.Handle can be whatever we like, so long as we are consistent.

   //This method takes in the URL path "/" and a function that takes in a response writer, and a http request.

   http.HandleFunc("/" , func(w http.ResponseWriter, r *http.Request) {

      //Takes the name from the URL query e.g ?name=Martin, will set welcome.Name = Martin.
      if name := r.FormValue("name"); name != "" {
         welcome.Name = name;
      }
      //If errors show an internal server error message
      //I also pass the welcome struct to the welcome-template.html file.
      if err := templates.ExecuteTemplate(w, "welcome-template.html", welcome); err != nil {
         http.Error(w, err.Error(), http.StatusInternalServerError)
      }
   })
    //Start the web server, set the port to listen to 8080. Without a path it assumes localhost
   //Print any errors from starting the webserver using fmt
   fmt.Println("Listening");
   fmt.Println(http.ListenAndServe(":8080", nil));
}