First Training

// main.go

package main

import (
  "encoding/json"
  "fmt"
  "log"
  "net/http"
  "os"
  "strings"
)

func handleListEnv(w http.ResponseWriter, r *http.Request) {
  w.Header().Set("Content-Type", "application/json")
  env := make(map[string]string)

  for _, pair := range os.Environ() {
    l := strings.Split(pair, "=")
    env[l[0]] = l[1]
  }
  result, err := json.Marshal(env)
  if err != nil {
    http.Error(w, "Error preparing the env", 500)
    return
  }
  w.Write(result)
}

func handleWelcome(w http.ResponseWriter, r *http.Request) {
  who := r.URL.Query().Get("who")
  if who == "" {
    fmt.Fprintf(w, "Hello World!")
    return
  }

  fmt.Fprintf(w, "Hello %s!!", who)
}

func main() {
  http.HandleFunc("/env", handleListEnv)
  http.HandleFunc("/welcome", handleWelcome)

  port := os.Getenv("LISTENING_PORT")
  if port == "" {
    port = "80"
  }
  addr := fmt.Sprintf(":%s", port)
  log.Printf("Starting server at %s", addr)

  err := http.ListenAndServe(addr, nil)
  if err != nil {
    log.Fatalf("Failed to start http server:%v", err)
  }
}

export CGO_ENABLED=0
go build -o hello main.go

LISTENING_PORT=8080 ./hello

// Dockerfile
FROM alpine
RUN apk update && apk add ca-certificates curl && rm -rf /var/cache/apk

WORKDIR /hello
ADD hello .

CMD ["./hello"]

sudo docker build -t hello:1.0 .

sudo docker run hello:1.0

sudo docker exec -it  sh

curl http://localhost/env; echo

sudo docker run -p 8080:80 -d hello:1.0

for i in $(seq 1 50)
do
  sudo docker run -p $((i+8080)):80 -d hello:1.0
done