回答discordgo用

ansIoReader.go

package main

import (
	"bufio"
	"log"
	"os"
	"time"
)

type User struct {
	name   string
	msg    chan []byte
	Active bool

	buf   []byte
	start int // buf用
	end   int // buf用
	off   int // 紀錄Read當前讀到哪個位子
}

const startBufSize = 1024

func NewUser(name string) *User {
	u := &User{name: name,
		msg:    make(chan []byte),
		buf:    make([]byte, 0),
		Active: true,
	}
	go u.listenMsg()
	return u
}

func (u *User) Read(b []byte) (n int, err error) {
	n = copy(b, u.buf[u.off:])
	u.off += n
	return n, nil
}

func (u *User) listenMsg() {
	for {
		select {
		case msg, isOpen := <-u.msg:
			if !isOpen {
				return
			}

			if !u.Active {
				break
			}

			if u.end == len(u.buf) { // buffer full, so, resize
				// https://github.com/golang/go/blob/8fb9565832e6dbacaaa057ffabc251a9341f8d23/src/bufio/scan.go#L189-L209
				newSize := len(u.buf) * 2
				if newSize == 0 {
					newSize = startBufSize
				}
				newBuf := make([]byte, newSize)
				copy(newBuf, u.buf[u.start:u.end])
				u.buf = newBuf
				u.end -= u.start
				u.start = 0
			}
			n := copy(u.buf[u.end:len(u.buf)], msg)
			u.end += n
		}
	}
}

type Hub struct {
	userList   map[*User]bool
	Register   chan *User
	Unregister chan *User
	Broadcast  chan []byte
	closed     bool
}

func NewHub() *Hub {
	return &Hub{
		userList:   make(map[*User]bool),
		Register:   make(chan *User),
		Unregister: make(chan *User),
		Broadcast:  make(chan []byte),
	}
}

func (h *Hub) Run() {
	for {
		if h.closed {
			return
		}
		select {
		case user, isOpen := <-h.Register:
			if !isOpen {
				return
			}
			h.userList[user] = true
		case user, isOpen := <-h.Unregister:
			if !isOpen {
				return
			}
			h.deleteUser(user)
		case data, isOpen := <-h.Broadcast:
			if !isOpen {
				return
			}
			for u := range h.userList {
				if !u.Active {
					continue
				}
				select {
				case u.msg <- data:
				case <-time.After(3 * time.Second):
					log.Printf("此資料無法傳給使用者:%s 故將此使用者刪除\n", u.name)
					h.deleteUser(u)
				}
			}
		}
	}
}

func (h *Hub) deleteUser(u *User) {
	u.Active = false
	close(u.msg)
	delete(h.userList, u)
}

func (h *Hub) Release() {
	for u := range h.userList {
		h.deleteUser(u)
	}
	close(h.Unregister)
	close(h.Register)
	h.closed = true
}

func main() {
	hub := NewHub()
	defer hub.Release()
	userCarson := NewUser("Carson")
	userFoo := NewUser("Foo")

	go hub.Run()

	hub.Register <- userCarson
	hub.Register <- userFoo

	// Test
	go func() {
		<-time.After(4 * time.Second)
		buf := make([]byte, 5)
		_, _ = userCarson.Read(buf)
		log.Printf("%s: %s\n", userCarson.name, buf)

		<-time.After(8 * time.Second)
		buf = make([]byte, 20)
		_, _ = userCarson.Read(buf)
		log.Printf("%s: %s\n", userCarson.name, buf)

		buf = make([]byte, 1024)
		_, _ = userFoo.Read(buf)
		log.Printf("%s: %s\n", userFoo.name, buf)
		log.Println("請輸入退出: -1")

		return
	}()

	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		text := scanner.Text()
		if text == "quit" || text == "exit" || text == "-1" {
			return
		}
		hub.Broadcast <- []byte(text)
	}
}