Advanced configuration with the golang Viper lib

Question

I'm working on my first real Go project and have been searching for some tools to handle the configuration.

Finally, I've found this tool: https://github.com/spf13/viper which is really nice but I have some issues when I try to handle some more complex configurations such as the following config.yaml example:

app:
  name: "project-name"
  version 1

models:
  modelA:
    varA: "foo"
    varB: "bar"

  modelB:
    varA: "baz"
    varB: "qux"
    varC: "norf"

I don't know how to get the values from modelB for example. While looking at the lib code, I've found the followings but I don't really understand how to use it:

// Marshals the config into a Struct
func Marshal(rawVal interface{}) error {...}

func AllSettings() map[string]interface{} {...}

What I want is to be able, from everywhere in my package, to do something like:

modelsConf := viper.Get("models")
fmt.Println(modelsConf["modelA"]["varA"])

Could someone explain me the best way to achieve this?

Answer 1

Since the "models" block is a map, it's a bit easier to call

m := viper.GetStringMap("models")

m will be a map[string]interface {}

Then, you get the value of m[key], which is an interface {}, so you cast it to map[interface {}]interface {} :

m := v.GetStringMap("models")
mm := m["modelA"].(map[interface{}]interface{})

Now you can access "varA" key passing the key as an interface {} :

mmm := mm[string("varA")]

mmm is foo

Answer 2

You can simply use:

m := viper.Get("models.modelA")

or

newViperForModelA := viper.Sub("models").Sub("modelA")