Viper can read environment changes when configuration files do not exist

[GuoxinL]

Environment variables

FOO.COO=321

test.yaml

foo:
  boo: aa
#  coo: 123
  doo:
    - abc
    - 123
    - Puff

config.go

func TestInit(t *testing.T) {
        a := viper.New()
	a.SetConfigName(configName)
	a.SetConfigType(configType)
	a.AddConfigPath(configPath)
        _ := a.ReadInConfig()
	ins := struct {
		Foo struct {
			Boo string   `yaml:"boo" mapstructure:"BOO"`
			Coo int      `yaml:"coo" mapstructure:"COO"`
			Doo []string `yaml:"doo"`
		} `yaml:"foo" mapstructure:"FOO"`
	}{}
        err = a.Unmarshal(&ins)
        fmt.Println(ins)
}

In the actual test, I did not read the parameters from the environment variables. What should I do?

[github-actions]

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[StefanSchoof]

Is this same problem as in #935?