.go

package main

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

func main() {
  http.HandleFunc("/boom", func(res http.ResponseWriter, req *http.Request) {
    res.WriteHeader(500)
    res.Write([]byte("Boom!"))
  })
  go http.ListenAndServe(":9000", nil)

  res, err := http.Get("http://127.0.0.1:9000/boom")
  if err != nil {
    log.Fatal(err)
  }
  fmt.Printf("res.StatusCode: %d\n", res.StatusCode)
}