Script to extract unique emails from file, assuming there is only one per line

emailExtract.go

package main

import (
	"bufio"
	"os"
	"regexp"
)

func checkErr(err error) {
	if err != nil {
		panic(err)
	}
}

func main() {
	readFileName := "FirstEmailsWT.rtf"
	writeFileName := "sortedEmails.txt"

	// email extract regex
	emailReg := regexp.MustCompile(`[a-zA-Z0-9-_.]+@[a-zA-Z0-9-_.]+`)
	// file to write sorted emails
	write, err := os.Create(writeFileName)
	checkErr(err)
	defer write.Close()
	// file to read from
	read, err := os.Open(readFileName)
	checkErr(err)
	defer read.Close()
	// map to keep only unique emails
	sorted := map[string]struct{}{}
	// read from file and extract emails assuming there is only one per string
	scanner := bufio.NewScanner(read)
	for scanner.Scan() {
		line := scanner.Text()
		email := emailReg.FindString(line)
		sorted[email] = struct{}{}
	}
	checkErr(scanner.Err())
	// save sorted emails
	for em := range sorted {
		_, err := write.WriteString(em + "\n")
		checkErr(err)
	}
}