I’m trying to override AllInputChannels with an envvar. The main config is in config.yaml which is picked up fine.

Running the below code viper.Unmarshal() throws an error:

'AllInputChannels' expected a map, got 'string'

How should I present the value in the envvar so it’s recognised?

I’ve removed error checking code below for clarity, except where the error appears.

type ChannelMap struct {
    Team    string `mapstructure:"Team"`
    Channel string `mapstructure:"Channel"`
}

type AllInputChannels struct {
    Production []ChannelMap `mapstructure:"Production"`
    Staging    []ChannelMap `mapstructure:"Staging"`
}

type Config struct {
    AllInputChannels AllInputChannels `mapstructure:"AllInputChannels"`
}

func NewConfig() Config { return Config{} }

func Build() Config {
    conf := NewConfig()
    
    _ = os.Setenv("ALLINPUTCHANNELS", `{"staging":[{"team":"Foo","channel":"DEF456"}]}`)

    viper.AddConfigPath(".") // Local builds.
    viper.SetConfigName("config")
    viper.SetConfigType("yaml")

    _ = viper.BindEnv("AllInputChannels")

    _ = viper.ReadInConfig()

    err := viper.Unmarshal(&conf)
    if err != nil {
        fmt.Printf("unable to decode config, %v", err)
    }

    return conf, nil
}

func main() {
    _ = Build()
}