fatal error: concurrent map writes panic

[2tvenom]

Got panic
v1.3.1

fatal error: concurrent map writes

goroutine 9 [running]:
runtime.throw(0x1b7726c, 0x15)
        /usr/local/Cellar/go/1.11.2/libexec/src/runtime/panic.go:608 +0x72 fp=0xc00015a778 sp=0xc00015a748 pc=0x102cef2
runtime.mapassign_faststr(0x19e5e00, 0xc0001b25a0, 0xc0000d7280, 0x15, 0xc000250f68)
        /usr/local/Cellar/go/1.11.2/libexec/src/runtime/map_faststr.go:199 +0x3da fp=0xc00015a7e0 sp=0xc00015a778 pc=0x101442a
gitlab.__.com/__/__/vendor/github.com/spf13/viper.insensitiviseMap(0xc0001b25a0)
        /Users/__/golibs/src/gitlab.__.com/__/__/vendor/github.com/spf13/viper/util.go:87 +0x196 fp=0xc00015a8c0 sp=0xc00015a7e0 pc=0x152fbe6

[sagikazarmark]

Can you share some example code to reproduce the issue? Are you trying to use Viper from separate goroutines?

[stanislav-bios-baranov]

Got same problem, but race appears in a place, which is totally unexpected to face it: UnmarshalKey. My expectation was, that unmarshaling part of config into external struct, should not change any internal structures inside viper package.

Here is small test, which fails for me in 50% of cases:

package main

import (
	"fmt"
	"testing"

	"github.com/stretchr/testify/require"

	"github.com/spf13/afero"
	"github.com/spf13/viper"
)

type Setting struct {
	TestValue *string `json:"testValue,omitempty" mapstructure:"testvalue"`
}

func TestConcurrency(t *testing.T) {

	content := []byte(`{"settings": {"A": {"value": "value A"}, "B": {"value": "value B"}}}`)

	aferoFS := afero.NewMemMapFs()
	require.NoError(t, afero.WriteFile(aferoFS, "conf.json", content, 0755))

	v := viper.New()

	v.SetConfigType("json")
	v.SetFs(aferoFS)
	v.SetConfigFile("conf.json")
	require.NoError(t, v.ReadInConfig())

	for i := 1; i < 100; i++ {
		t.Run(fmt.Sprintf("flow #%d", i), func(tt *testing.T) {
			tt.Parallel()
			settings := make(map[string]*Setting)
			require.NotPanics(t, func() {
				require.NoError(t, v.UnmarshalKey("settings", &settings))
			})
		})
	}

}

In my case problem is with insensitiviseMaps call from UnmarshalKey ( https://github.com/spf13/viper/blob/master/viper.go#L1582 )

[moorereason]

Is this fixed by 9e56dac?