Viper PFlag nested binding

README.md

• go run main.go -c app.yml works as expected and unmarshalls Remote.Host="a good host"
• go run main.go -c app.yml -n "new host" seems to have the correct structure when calling AllSettings, but unmarshal doesn't get set from the command line
• go run main.go -c no-app.yml panics
• go run main.go -c no-app.yml -n "new host" panics
• go run main.go -n "new host" panics
• go run main.go panics

panic

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0xd0 pc=0x750e25]

goroutine 1 [running]:
viper_test/vendor/github.com/spf13/viper.(*Viper).AllKeys(0x0, 0x30, 0x804c60, 0xc420175e01)
        viper_test/vendor/github.com/spf13/viper/viper.go:1582 +0x45
viper_test/vendor/github.com/spf13/viper.(*Viper).AllSettings(0x0, 0x7492d1)
        viper_test/vendor/github.com/spf13/viper/viper.go:1662 +0x51
viper_test/vendor/github.com/spf13/viper.(*Viper).Unmarshal(0x0, 0x781220, 0xc42009b060, 0x0, 0x0)
        viper_test/vendor/github.com/spf13/viper/viper.go:759 +0x2f
main.main()
        viper_test/main.go:36 +0x1bd
exit status 2

app.yml

app:
    remote:
        host: "a good host"

Gopkg.lock

[[projects]]
  name = "github.com/fsnotify/fsnotify"
  packages = ["."]
  revision = "c2828203cd70a50dcccfb2761f8b1f8ceef9a8e9"
  version = "v1.4.7"

[[projects]]
  branch = "master"
  name = "github.com/hashicorp/hcl"
  packages = [".","hcl/ast","hcl/parser","hcl/printer","hcl/scanner","hcl/strconv","hcl/token","json/parser","json/scanner","json/token"]
  revision = "ef8a98b0bbce4a65b5aa4c368430a80ddc533168"

[[projects]]
  name = "github.com/magiconair/properties"
  packages = ["."]
  revision = "c3beff4c2358b44d0493c7dda585e7db7ff28ae6"
  version = "v1.7.6"

[[projects]]
  branch = "master"
  name = "github.com/mitchellh/mapstructure"
  packages = ["."]
  revision = "00c29f56e2386353d58c599509e8dc3801b0d716"

[[projects]]
  name = "github.com/pelletier/go-toml"
  packages = ["."]
  revision = "acdc4509485b587f5e675510c4f2c63e90ff68a8"
  version = "v1.1.0"

[[projects]]
  name = "github.com/spf13/afero"
  packages = [".","mem"]
  revision = "63644898a8da0bc22138abf860edaf5277b6102e"
  version = "v1.1.0"

[[projects]]
  name = "github.com/spf13/cast"
  packages = ["."]
  revision = "8965335b8c7107321228e3e3702cab9832751bac"
  version = "v1.2.0"

[[projects]]
  branch = "master"
  name = "github.com/spf13/jwalterweatherman"
  packages = ["."]
  revision = "7c0cea34c8ece3fbeb2b27ab9b59511d360fb394"

[[projects]]
  name = "github.com/spf13/pflag"
  packages = ["."]
  revision = "583c0c0531f06d5278b7d917446061adc344b5cd"
  version = "v1.0.1"

[[projects]]
  name = "github.com/spf13/viper"
  packages = ["."]
  revision = "b5e8006cbee93ec955a89ab31e0e3ce3204f3736"
  version = "v1.0.2"

[[projects]]
  branch = "master"
  name = "golang.org/x/sys"
  packages = ["unix"]
  revision = "79b0c6888797020a994db17c8510466c72fe75d9"

[[projects]]
  name = "golang.org/x/text"
  packages = ["internal/gen","internal/triegen","internal/ucd","transform","unicode/cldr","unicode/norm"]
  revision = "f21a4dfb5e38f5895301dc265a8def02365cc3d0"
  version = "v0.3.0"

[[projects]]
  name = "gopkg.in/yaml.v2"
  packages = ["."]
  revision = "5420a8b6744d3b0345ab293f6fcba19c978f1183"
  version = "v2.2.1"

[solve-meta]
  analyzer-name = "dep"
  analyzer-version = 1
  inputs-digest = "687b252626f2925730598945dd483d5b8e544e202167f2ecff05239289073e91"
  solver-name = "gps-cdcl"
  solver-version = 1

Gopkg.toml

[[constraint]]
  name = "github.com/spf13/pflag"
  version = "1.0.1"

[[constraint]]
  name = "github.com/spf13/viper"
  version = "1.0.2"

main.go

package main

import (
	"log"

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

type opts struct {
	Remote struct {
		Host string
	}
}

func main() {
	failOnError := func(err error) {
		if err != nil {
			log.Fatal(err)
		}
	}

	cfg := pflag.StringP("config", "c", "", "config to load from")

	pflag.StringP("host", "n", "", "a hostname")
	failOnError(viper.BindPFlag("app.remote.host", pflag.Lookup("host")))

	pflag.Parse()

	if *cfg != "" {
		viper.SetConfigFile(*cfg)
		failOnError(viper.ReadInConfig())
	}

	var o opts
	failOnError(viper.Sub("app").Unmarshal(&o))
	log.Printf("%#v", viper.AllSettings())
	log.Printf("%#v", o)
}

no-app.yml

remote:
    host: "a good host"