Golang Streaming Server

streaming.go

package main

import (
	"fmt"
	"net/http"
	"sync"
	"time"
)

func main() {
	// create a global counter and a mutex for it
	mutex := sync.Mutex{}
	i := 1

	http.HandleFunc("/", func(rw http.ResponseWriter, req *http.Request) {
		mutex.Lock()
		index := i
		i++
		mutex.Unlock()

		// the function sending text during execution
		var waitingText func(string)
		// the function sending text that is not time critical
		var contentText func(string)

		if hj, ok := rw.(http.Hijacker); ok {
			// hijack the connection
			if con, bufrw, err := hj.Hijack(); err != nil {
				http.Error(rw, fmt.Sprintf("Could not hijack connection: %v.", err.Error()), http.StatusInternalServerError)
				return
			} else {
				// we are now responsible for the connection and its data flow
				// so make sure to close the connection in the end
				defer con.Close()
				// and also flush all pending data to the client
				defer bufrw.Flush()

				contentText = func(input string) {
					// simply send the text
					if length, err := bufrw.WriteString(input); err != nil {
						panic(err)
					} else {
						fmt.Printf("Sent %q (%v bytes).\n", input, length)
					}
				}
				waitingText = func(input string) {
					// send the text
					contentText(input)
					// make sure it is immediately flushed to the client
					if err := bufrw.Flush(); err != nil {
						panic(err)
					}

					fmt.Printf("Sent waiting text.\n")
				}
			}
		} else {
			fmt.Printf("Streaming not supported.\n")
			waitingText = func(input string) {
				// nothing
				rw.WriteHeader(http.StatusOK)
			}
			contentText = func(input string) {
				rw.Write([]byte(input))
			}
		}

		// user-interaction
		fmt.Printf("Request %v received.\n", index)
		waitingText(fmt.Sprintf("Welcome Nr.%v. Plase wait...\n", index))

		select {
		case <-time.After(3 * time.Second):
			contentText("\n")
			contentText("Hello World\n")

			fmt.Printf("Request %v responded to.\n", index)
		}
	})

	// start the server
	done := make(chan bool)
	go func() {
		err := http.ListenAndServe(":3000", nil)
		fmt.Printf("Server crashed: %v.", err)

		done <- true
	}()
	fmt.Printf("Server started!\n")
	<-done
}