How to parse and extract MIME headers from an email message in Go?

To parse and extract MIME headers from an email message in Go, you can use the net/mail package. Here's an example:

package main

import (
	"fmt"
	"io/ioutil"
	"net/mail"
)

func main() {
	// Read the email message from a file or any other source
	emailContent, err := ioutil.ReadFile("email.eml")
	if err != nil {
		fmt.Println("Failed to read email:", err)
		return
	}

	// Parse the email
	message, err := mail.ReadMessage(emailContent)
	if err != nil {
		fmt.Println("Failed to parse email:", err)
		return
	}

	// Extract the MIME headers
	headers := message.Header
	for key, values := range headers {
		// If there are multiple values for a header, they will be returned as a slice
		for _, value := range values {
			fmt.Printf("%s: %s\n", key, value)
		}
	}
}

In this example, we read the email content from a file using ioutil.ReadFile, then we pass the content to mail.ReadMessage to parse the email. The ReadMessage function returns a *mail.Message object that contains the message's MIME headers.

We can then access the headers using the Header field of the Message object. It returns a mail.Header object, which is essentially a map of string keys to slices of string values. We iterate over the headers and their values to print them out.

Make sure to replace "email.eml" with the actual path or source of your email message.