03. Stream Of Letters

package main

import "fmt"

func main() {
    var input, word, message string
    fmt.Scanln(&input)

    var c = 0
    var o = 0
    var n = 0

    for ; input != "End"; {
        var letter = input[0]
        if letter >= 'A' && letter <= 'Z' || letter >= 'a' && letter <= 'z' {
            if letter == 'c' && c == 0 {
                c++
            } else if letter == 'o' && o == 0 {
                o++
            } else if letter == 'n' && n == 0 {
                n++
            } else {
                word += string(letter)
            }

            if c == 1 && o == 1 && n == 1 {
                c--
                o--
                n--
                message += word + " "
                word = ""
            }
        }
        fmt.Scanln(&input)
    }

    fmt.Println(message)
}

ИЛИ:

package main

import (
    "fmt"
    "strings"
)

func main() {
    const alpha = "abcdefghijklmnopqrstuvwxyz"

    var input, word, message string
    var secretWord = "con"
    fmt.Scanln(&input)

    for ; input != "End"; {
         if strings.Contains(secretWord, input) {
            secretWord = strings.Replace(secretWord, input, "", 1)
            if secretWord == "" {
                secretWord = "con"
                message += word + " "
                word = ""
            }
        } else if strings.Contains(alpha, strings.ToLower(input)) {
            word += input
        }
        fmt.Scanln(&input)
    }

    fmt.Println(message)
}