Fibers in Go (found at https://play.golang.org/p/NSIlZ327sC)

fiber.go

// I found the following implementation (verbatim) of Fibers in Go at https://play.golang.org/p/NSIlZ327sC
// I'm capturing it here for future reference.

package main

import (
	"errors"
	"fmt"
)

var errResumeDeadFiber = errors.New("resume dead fiber")

type fiberDeadPanic struct{}

type Fiber struct {
	resume chan int
	close  chan int
}

func NewFiber() *Fiber {
	f := Fiber{
		resume: make(chan int),
		close:  make(chan int),
	}
	go f.run()
	return &f
}

func (f *Fiber) handleBreak() {
	if r := recover(); r != nil {
		if _, ok := r.(fiberDeadPanic); !ok {
			panic(r)
		}
	}
	fmt.Println("exit goroutine")
}

func (f *Fiber) run() {
	defer f.handleBreak()

	i := 0
	for {
		f.Yield(i)
		f.Yield(i)
		i++
	}
}

func (f *Fiber) Yield(i int) {
	select {
	case <-f.close:
		panic(fiberDeadPanic{})
	case f.resume <- i:
	}
}

func (f *Fiber) Resume() (int, error) {
	select {
	case <-f.close:
		return 0, errResumeDeadFiber
	default:
		return <-f.resume, nil
	}
}

func (f *Fiber) Close() {
	select {
	case <-f.close:
	default:
		close(f.close)
	}
}

func main() {
	for i := 0; i < 5; i++ {
		f := NewFiber()
		fmt.Println(f.Resume())
		fmt.Println(f.Resume())
		fmt.Println(f.Resume())
		fmt.Println(f.Resume())
		f.Close()
		fmt.Println(f.Resume())
	}
}