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() {
  router := gin.Default()

  router.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)
    }()
  })

  router.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
  router.Run(":8080")
}