This is a continuation from previous article How Does Web Work With Go Part 1. To talk with web server, you need to speak the same language. In this case it is protocol HTTP. Currently there are 3 version of this protocol in use: HTTP 1.1 - TCP text format HTTP 2 - TCP binary format HTTP 3 - UDP binary format In our case we will use HTTP 1.1 which is defined in RFC2616....
This evening I was wondering if my 5-year old son would ask me, what is the Internet and how it works, what I would reply to him? Maybe he is a bit young to go into the details, but I would like to explain what I know about it and to structure my knowledge and learn more in the process. Because as Seneka said: while we teach, we learn. I would like to dive deep into the details in this series with some Go examples....
I wanted to create a logging middleware for HTTP client. Working code example you can find on GitHub The basic structure is type LoggingTransport struct { rt http.RoundTripper } func (t *LoggingTransport) RoundTrip(r *http.Request) (*http.Response, error) { // do before request is sent, ex. start timer, log request resp, err := t.rt.RoundTrip(r) // do after the response is received, ex. end timer, log response return resp, err } I found this code in Kubernetes source and I liked this implementation, I decided to adjust it to my needs....
Recently I wanted to learn more about Go’s slog package. Also for some other project I needed to create an access logger. I could not find a solution so I decided to create my own. I was inspired by two solutions: rs/zerolog/hlog package great guide at betterstack Working code example can be found on GitHub Requirements In my logger I wanted to have all standard data: request duration, status code, bytes written, method, url, user agent, remote addr plus some extra...
When working on local environment, it is useful to use trusted TLS certificates. For this purpose we can use mkcert. mkcert automatically creates and installs a local CA in the system root store, and generates locally-trusted certificates. Working code example can be found on GitHub Instalation First we need to install it ❯ mkcert -install The local CA is already installed in the system trust store! 👍 The local CA is already installed in the Firefox trust store!...
This is an code based on opentelemetry dice example which uses rs/zerolog and adds trace id to logs. Working code example can be found on GitHub TraceIDHandler This is a standard access logger. What is extra here is traceID := traceIDHandler("trace_id", "span_id") traceIDHandler adds those two fields to zerolog if it finds them in context. func requestLogger(next http.Handler) http.Handler { h := hlog.NewHandler(logger) accessHandler := hlog.AccessHandler(func(r *http.Request, status, size int, duration time....
Graceful shutdown is a technique used to smoothly terminate an app. It allows the clients to receive data from the app. Also it gives time for the load balancer to deregister it and not send a traffic to it. // this is not an app with graceful shutdown package main import ( "fmt" "log" "net/http" "time" ) // this request takes long time to complete func indexHandler(w http.ResponseWriter, r *http.Request) { log....
Every application should contain at least two endpoints: readiness check, health check. Readiness check should indicate when the app is ready to serve traffic. It should allow traffic when the app is correctly initialized. For example it should wait for the database connection to be established. The connection to cache or external API as well. This probe allows to cut off the traffic in case the app is unable to handle it....
There are multiple ways to configure your Go application. I will describe a few most common one in this article with code samples. Flags Go supports command line flags with builtin package flag. package main import ( "flag" "log" "net/http" ) func main() { addrPtr := flag.String("addr", ":8000", "addr of http server") flag.Parse() log.Printf("Listening on %s", *addrPtr) log.Fatal(http.ListenAndServe(*addrPtr, nil)) } func main() { var addr string flag.StringVar(&addr, "addr", ":8000", "addr of http server") flag....
Serving static website in Go I would like to describe here how to serve static content with Go. Go http package provides handy function http.FileServer to serve such content. FileServer also allows to browse files when index.html is missing in a catalog. Preparing files Let’s create such structure. $ tree . ├── assets │ ├── page.html │ └── styles │ └── main.css └── main.go File: assets/page.html <!doctype html> <html> <head> <meta charset="utf-8"> <title>Document</title> <link rel="stylesheet" href="/styles/main....