package main

import (
    "fmt"
    "time"
)

func main() {
    ch := make(chan int, 2)

    // initiate +ve & -ve folks
    go iAcceptOnlyNegativeFolks(ch)
    go iAcceptOnlyPositiveFolks(ch)

    // ignite fire between +ve & -ve folks 😅
    ch <- 1

    // this is just simple way to block main else go routines will exit along with main
    time.Sleep(time.Millisecond * 5)

}

func iAcceptOnlyPositiveFolks(ch chan int) {
    for {
        select {
        case x := <-ch:
            if x > 0 {
                fmt.Println(x, " is a positive folk")
                ch <- x + 1
            } else {
                // giving some motivation to -ve folk to become +ve folk
                ch <- x * (-1)
            }
        }
    }
}

func iAcceptOnlyNegativeFolks(ch chan int) {
    for {
        select {
        case x := <-ch:
            if x < 0 {
                fmt.Println(x, " is a negative folk")
                ch <- x - 1
            } else {
                // giving some motivation to +ve folk to become -ve folk
                ch <- x * (-1)
            }
        }
    }
}

sample output 1:-
-1  is a negative folk
-2  is a negative folk
-3  is a negative folk
4  is a positive folk
-5  is a negative folk
-6  is a negative folk
7  is a positive folk
-8  is a negative folk
9  is a positive folk
10  is a positive folk
11  is a positive folk

sample output 2:-
1  is a positive folk
2  is a positive folk
3  is a positive folk
-4  is a negative folk
-5  is a negative folk
6  is a positive folk
7  is a positive folk