go_string_panic

go_string_panic.go

// panic: s should not be WHAT

// goroutine 1 [running]:
// main.main()
// 	main.go:44 +0x19c
// exit status 2

// panic: runtime error: invalid memory address or nil pointer dereference
// [signal SIGSEGV: segmentation violation code=0x2 addr=0x7 pc=0x102fa19a4]

// goroutine 1 [running]:
// main.main()
// 	main.go:48 +0x154
// exit status 2

main.go

package main

import (
	"fmt"
	"time"
)

const (
	STR1 = "WHAT THE"
	STR2 = "HELL"
	STR3 = ""
)

type A struct {
	s string
}

func main() {
	a := A{
		s: STR1,
	}
	go func() {
		i := 0
		fmt.Printf("len=%d %p\n", len(a.s), &a.s)
		for {
			switch i % 3 {
			case 0:
				a.s = STR1
			case 1:
				a.s = STR2
			case 2:
				a.s = STR3
			}
			time.Sleep(1)
			i++
		}
	}()
	count := 0
	for {
		s := a.str()
		if count == 0 {
			fmt.Printf("len=%d %p\n", len(s), &s)
		}
		if s == "WHAT" {
			panic("s should not be WHAT")
		}
		if len(s) > 0 {
			if s[len(s)-1] == 'E' {
				// fmt.Println(s)
				count++
			}
		}
		time.Sleep(1)
	}
	fmt.Println(count)
}

func (a *A) str() string {
	return a.s
}