Code kata. https://forum.lowyat.net/index.php?showtopic=3571866&view=findpost&p=75952192

dictionary.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"regexp"
	"sort"
	"strconv"
	"strings"
)

func main() {
	dict := make(map[string]bool)
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Scan()
	lines := scanner.Text()
	nlines, _ := strconv.Atoi(lines)

	re, _ := regexp.Compile("(?i)[a-z]+")
	for ; nlines > 0; nlines-- {
		scanner.Scan()
		line := scanner.Text()
		words := re.FindAllStringSubmatch(line, -1)
		for _, word := range words {
			lword := strings.ToLower(word[0])
			if re.MatchString(lword) {
				dict[lword] = true
			}
		}
	}
	keys := make([]string, 0, len(dict))
	for k, _ := range dict {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	fmt.Println(strings.Join(keys, "\n"))
}