golangflag: use goflag.DefValue

[holycheater]

The piece of code in question breaks priority behavior for spf13/viper, because the flag/env precedence order in viper is actually flag, env, default flag.

func main() {
	var s string
	flag.StringVar(&s, "param", "def value", "")
	flag.Parse()
	pflag.CommandLine.AddGoFlagSet(flag.CommandLine)
	viper.BindPFlags(pflag.CommandLine)
	viper.AutomaticEnv()
	log.Println(viper.GetString("param"))
}

PARAM=foo go run ./main.go -param bar // expecting flag param to have higher priority than env param
9/03/14 20:02:06 foo

[CLAassistant]

All committers have signed the CLA.

[therealmitchconnors]

Can you add a regression test for this behavior?