Goroutines inside a middleware

When starting new Goroutines inside a middleware or handler, you SHOULD NOT use the original context inside it, you have to use a read-only copy.

func main() {
    r := gin.Default()

    r.GET("/long_async", func(c *gin.Context) {
        // create copy to be used inside the goroutine
        cCp := c.Copy()
        go func() {
            // simulate a long task with time.Sleep(). 5 seconds
            time.Sleep(5 * time.Second)

            // note that you are using the copied context "cCp", IMPORTANT
            log.Println("Done! in path " + cCp.Request.URL.Path)
        }()
    })

    r.GET("/long_sync", func(c *gin.Context) {
        // simulate a long task with time.Sleep(). 5 seconds
        time.Sleep(5 * time.Second)

        // since we are NOT using a goroutine, we do not have to copy the context
        log.Println("Done! in path " + c.Request.URL.Path)
    })

    // Listen and serve on 0.0.0.0:8080
    r.Run(":8080")
}