CODEWITHSUNDEEP
apigostreaminggoroutinego-gin
kunalag
kunalag

Reputation: 151

How to write a stream API using gin-gonic server in golang? Tried c.Stream didnt work

I wanted to create one streaming API using gin-gonic server in golang.

func StreamData(c *gin.Context) {
    chanStream := make(chan int, 10)
    go func() {for i := 0; i < 5; i++ {
        chanStream <- i
        time.Sleep(time.Second * 1)
    }}()
    c.Stream(func(w io.Writer) bool {
        c.SSEvent("message", <-chanStream)
        return true
    })
}

router.GET("/stream", controller.StreamData)

But when I am trying to hit the endpoint, it just stucks and no response comes. Has someone used the stream function so that he/she can point the mistake which I might be doing. Thanks!

Upvotes: 15

Views: 20118

Answers (1)

mattn
mattn

Reputation: 7733

You should return false if the stream ended. And close the chan.

package main

import (
    "io"
    "time"

    "github.com/gin-gonic/contrib/static"
    "github.com/gin-gonic/gin"
    "github.com/mattn/go-colorable"
)

func main() {
    gin.DefaultWriter = colorable.NewColorableStderr()
    r := gin.Default()
    r.GET("/stream", func(c *gin.Context) {
        chanStream := make(chan int, 10)
        go func() {
            defer close(chanStream)
            for i := 0; i < 5; i++ {
                chanStream <- i
                time.Sleep(time.Second * 1)
            }
        }()
        c.Stream(func(w io.Writer) bool {
            if msg, ok := <-chanStream; ok {
                c.SSEvent("message", msg)
                return true
            }
            return false
        })
    })
    r.Use(static.Serve("/", static.LocalFile("./public", true)))
    r.Run()
}

Additional

Client code should be:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
<script>
var stream = new EventSource("/stream");
stream.addEventListener("message", function(e){
    console.log(e.data);
});
</script>    
</body>
</html>

Upvotes: 21

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