create a http server and add a custom header to the response in go

To create an HTTP server and add a custom header to the response in Go, you can follow these steps:

• Import the net/http package
• Create a handler function to return the response
• Add a custom header using the w.Header().Set() method inside the handler function
• Start the server using the http.ListenAndServe() method

Here's an example code snippets to illustrate it:

main.go
package main

import (
	"fmt"
	"net/http"
)

func handler(w http.ResponseWriter, r *http.Request) {
	// Set the custom header
	w.Header().Set("X-Custom-Header", "Hello, World!")
	
	// Write the response body
	fmt.Fprintf(w, "Hello, World!")
}

func main() {
	// Register the handler function
	http.HandleFunc("/", handler)

	// Start the server
	err := http.ListenAndServe(":8080", nil)
	if err != nil {
		panic(err)
	}
}
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In this example, the handler function is registered to the root endpoint ("/") using the http.HandleFunc() method. Inside the handler function, we set a custom header using the w.Header().Set() method and write the response body using the fmt.Fprintf() method.

When the server starts using the http.ListenAndServe() method, it listens on port 8080.