Minimal fanout pattern implemented with goroutine

fanout.go

package main

import (
	"context"
	"sync"
)

// FanOutContext contains fanout data
type FanOutContext struct {
	channels []chan interface{}
	mutex    *sync.Mutex
}

// NewFanOutContext creates new fanout context
func NewFanOutContext() *FanOutContext {
	var channels []chan interface{}
	return &FanOutContext{
		channels: channels,
		mutex:    &sync.Mutex{},
	}
}

// Run starts receiving data from sourceChan and fanning out. This function should be called as a goroutine
func (foc *FanOutContext) Run(fanOutCtx context.Context, sourceChan chan interface{}) {
	for {
		select {
		case <-fanOutCtx.Done():
			return
		case data := <-sourceChan:
			foc.mutex.Lock()
			for _, channel := range foc.channels {
				channel <- data
			}
			foc.mutex.Unlock()
		}
	}
}

// AddChannel adds new channel to be fanned out. The returned index should be kept for calling RemoveAndCloseChannel(index)
func (foc *FanOutContext) AddChannel() (chan interface{}, int) {
	index := len(foc.channels)
	channel := make(chan interface{}, 1)
	foc.mutex.Lock()
	foc.channels = append(foc.channels, channel)
	foc.mutex.Unlock()
	return channel, index
}

// RemoveAndCloseChannel removes and closes channel at index
func (foc *FanOutContext) RemoveAndCloseChannel(index int) {
	close(foc.channels[index])
	foc.mutex.Lock()
	foc.channels = append(foc.channels[:index], foc.channels[index+1:]...)
	foc.mutex.Unlock()
}