server.go

package main

import (
	"fmt"
	"net/http"
	"runtime/pprof"
	"sync"
)

var (
	total int
	mutex sync.Mutex
)

// allocate a megabyte in a goroutine that blocks forever
func allocateMegabyte() int {
	go func() {
		var mb [131072]int64
		_ = mb
		select {}
	}()
	mutex.Lock()
	defer mutex.Unlock()
	total++
	return total
}

func main() {

	http.HandleFunc("/allocate", func(w http.ResponseWriter, r *http.Request) {
		tot := allocateMegabyte()
		if _, err := fmt.Fprintf(w, "total: %d mb", tot); err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
		}
	})

	http.HandleFunc("/dump", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/binary")
		if err := pprof.WriteHeapProfile(w); err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
		}
	})

	http.ListenAndServe(":8080", nil)
}