package main

import (
    "log"
    "math/rand"
    "strconv"
)

func worker(input <-chan string, output chan<- string) {
    defer close(output)

    bufer := make(map[string]bool)

    for data := range input {
        if data == ":reset" {
            bufer = make(map[string]struct{})
        }

        if _, has := bufer[data]; has {
            continue
        }

        bufer[data] = true

        output <- data
    }
}

func reader(data <-chan string, done chan<- struct{}) {
    defer close(done)

    for row := range data {
        log.Println("received", row)
    }
}

func main() {
    input := make(chan string)
    output := make(chan string)

    go worker(input, output)

    done := make(chan struct{})
    go reader(output, done)

    for i := 0; i < 10; i++ {
        data := strconv.Itoa(rand.Intn(10))
        log.Println("sent", data)

        input <- data
    }
    close(input)

    <-done
}