slice_test.go

package main

import (
	"log"
	"testing"

	"golang.org/x/sync/errgroup"
)

type action func() error

type hasAction struct {
	actions []action
}

func (h *hasAction) AddAction(act action) {
	h.actions = append(h.actions, act)
}

func TestSlice(t *testing.T) {
	if err := syncTest(t); err != nil {
		t.Error(err)
	}
	for i := 0; i < 1000; i++ {
		if err := asyncTest(t); err != nil {
			t.Error(err)
		}
	}
}

func syncTest(t *testing.T) error {
	h := &hasAction{}
	for i := 0; i < 10; i++ {
		n := i
		h.AddAction(func() error {
			log.Print(n)
			return nil
		})
	}
	return nil
}
func asyncTest(t *testing.T) error {
	var eg errgroup.Group
	h := &hasAction{}
	for i := 0; i < 10; i++ {
		n := i
		eg.Go(func() error {
			h.AddAction(func() error {
				log.Print(n)
				return nil
			})
			return nil
		})
	}
	return eg.Wait()
}

何回か回すと SEGVする

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x110da0b]

goroutine 137137 [running]:
command-line-arguments.(*hasAction).AddAction(...)