在Websocket中使用频道

Question

If I use a chan anywhere on main or func home, the application runs, but it doesn't really work. No errors thrown, however, it won't work. If I remove the channels references, it goes back to working. Either by using a chan in a struct or a global channel the application stops working.

In a GET request, it returns h.Message from func home by adding any channel in the code, GET request wont return the message.

https://play.golang.org/p/-ZVcLhZRRRG

package main

import (
    "fmt"
    "net/http"

    "github.com/gorilla/websocket"
    // _ "github.com/go-sql-driver/mysql"
)

type WMessage struct {
    Message string `json:"message"`
    ch      chan string
}

var upgrader = websocket.Upgrader{
    ReadBufferSize:  1024,
    WriteBufferSize: 1024,
    CheckOrigin: func(r *http.Request) bool {
        return true
    },
}

var Chann chan string

func (h *WMessage) home(w http.ResponseWriter, r *http.Request) {
    h.Message = "hey this is the message from home"

    fmt.Fprintln(w, h.Message)
    fmt.Println(<-h.ch)
}

func main() {
    hom := &WMessage{}

    hom.ch = make(chan string)

    hom.ch <- "message sent"

    http.HandleFunc("/", hom.home)
    err := http.ListenAndServe(":3000", nil)
    if err != nil {
        fmt.Println("there was an error -> ", err)
    }
}

Answer 1

Unbuffered channels are blocking in nature, i.e. writing to channel (hom.ch <- "message sent") and reading from channel (fmt.Println(<-h.ch)) block the go-routine.

In your case, http server is not running because hom.ch <- "message sent" blocks the execution. That's why GET request is not working.

One simple solution can be to make it buffered channel instead.