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Golang: Building a Basic Web Server in Go

Continuing with our #golang-tutorial blog series, in this post we will setup a Basic HTTP Server in Go.

Our Web Server:

Our Web Server will respond on 2 Request Paths:

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- / -> returns "Hello, Wolrd!"
- /cheers -> returns "Goodbye!"

Application Code:

If you have not setup your golang environment, you can do so by visiting @AkyunaAkish’s Post on Setting up a Golang Development Enviornment on MacOSX.

Create the server.go or any filename of your choice. Note: I created 2 ways of returning the content of http response for demonstration

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package main

import (
  "io"
        "log"
  "net/http"
)

func hello(w http.ResponseWriter, r *http.Request) {
  w.Header().Set("Content-Type", "text/plain; charset=utf-8")
  w.WriteHeader(http.StatusOK)
  w.Write([]byte("Hello, World!" + "\n")
  log.Println("hello function handler was executed")
}

func goodbye(w http.ResponseWriter, r *http.Request) {
  w.Header().Set("Content-Type", "text/plain; charset=utf-8")
  w.WriteHeader(http.StatusOK)
  io.WriteString(w, "Cheers!" + "\n")
  log.Println("goodbye function handler was executed")
}

func main() {
  http.HandleFunc("/", hello)
  http.HandleFunc("/cheers", goodbye)
  http.ListenAndServe(":8000", nil)
}

Explanation of what we are doing:

  • Programs runs in the package main
  • We are importing 3 packages: io, log and net/http
  • HandleFunc registers the handler function for the given pattern in the DefaultServeMux, in this case the HandleFunc registers / to the hello handler function and /cheers to the goodbye handler function.
  • In our 2 handler functions, we have two arguments:
    • The first one is http.ResponseWriter and its corresponding response stream, which is actually an interface type.
    • The second is *http.Request and its corresponding HTTP request. io.WriteString is a helper function to let you write a string into a given writable stream, this is named the io.Writer interface in Golang.
  • ListenAndServe starts an HTTP server with a given address and handler. The handler is usually nil, which means to use DefaultServeMux
  • The logging is not a requirement, but used it for debugging/verbosity

Running our Server:

Run the http server:

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$ go run server.go

Client Side Requests:

Run client side http requests to your golang web server:

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$ curl -i http://localhost:8000/
HTTP/1.1 200 OK
Content-Type: text/plain; charset=utf-8
Date: Wed, 21 Nov 2018 21:33:42 GMT
Content-Length: 14

Hello, World!

And another request to /cheers:

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$ curl -i http://localhost:8000/cheers
HTTP/1.1 200 OK
Content-Type: text/plain; charset=utf-8
Date: Wed, 21 Nov 2018 21:29:46 GMT
Content-Length: 8

Cheers!

Server Side Output:

As we used the log package, the logging gets returned to stdout:

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$ go run server.go
2018/11/21 23:29:36 hello function handler was executed
2018/11/21 23:29:46 goodbye function handler was executed

Resources:

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