toml.Unmarshal overrides origin values even if not export field

[For-ACGN]

Describe the bug
toml.Unmarshal overrides origin values even if not export field

To Reproduce

package main

import (
	"fmt"
	"log"

	"github.com/pelletier/go-toml"
)

type Ti interface {
	Print()
}

type tii struct {
	A string
}

func (this *tii) Print() {
	fmt.Print(this.A)
}

type S struct {
	A  string
	ti Ti
	tp *tii
}

func main() {
	ti := new(tii)
	tp := new(tii)
	s := &S{A: "asd", ti: ti, tp: tp}
	b, err := toml.Marshal(s)
	if err != nil {
		log.Fatalln(err)
	}
	fmt.Printf("%p %p %p \n", &s.A, s.ti, s.tp)
	toml.Unmarshal(b, s)
	fmt.Printf("%p %p %p \n", &s.A, s.ti, s.tp)
	ti.Print()
	tp.Print()
	s.ti.Print()
	s.tp.Print()
}

print

0xc0000884e0 0xc00005e4c0 0xc00005e4d0
0xc0000884e0 %!p(<nil>) 0x0
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x18 pc=0x4eea54]

goroutine 1 [running]:
main.main()
        E:/Project/toml bug/toml.go:41 +0x4a4
exit status 2

Expected behavior
not set nil

Versions

• go-toml: v1.4.0 and dba45d4
• go: version 1.12.5
• operating system: Windows

[pelletier]

Thanks for the bug report! Looks like #284 will fix that problem as soon as it's merged (it does work for this specific example).

[pelletier]

@For-ACGN #284 has been merged. Do you mind giving this another shot to make sure the bug is fixed for you?

[For-ACGN]

@pelletier @roberth-k
Oh! It fix this bug and works right. Thank you!
https://github.com/For-ACGN/go-toml-test