https://play.golang.org/p/pUAEH141Bp

README.md

わからないエラーが出る。

$ go run main.go                                                                                                   1 ↵
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x2167]

goroutine 1 [running]:
panic(0x8ef00, 0xc42000a0c0)
	/usr/local/opt/go/libexec/src/runtime/panic.go:500 +0x1a1
main.main()
	/tmp/main.go:26 +0x127
exit status 2

適当に調べて最適化を切ってみる。

$ go run -gcflags '-N -l' main.go                                                                                  1 ↵
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x2085]

goroutine 1 [running]:
panic(0x8f020, 0xc42000a0c0)
	/usr/local/opt/go/libexec/src/runtime/panic.go:500 +0x1a1
main.(*Sample).Method(0x0)
	/tmp/main.go:13 +0x45
main.main()
	/tmp/main.go:26 +0x7e
exit status 2

わかるエラーになった(わかる

main.go

package main

import (
	"fmt"
)

type Sample struct {
	Foo string
}

func (v *Sample) Method() {
	if v == nil {
		*v = Sample{}
	}
	if v.Foo == "" {
		v.Foo = "Foo"
	}
}

func main() {
	var v1 *Sample
	v2 := &Sample{
		Foo: "Bar",
	}

	v1.Method()
	v2.Method()

	fmt.Println(v1)
	fmt.Println(v2)
}