How Can I Efficiently Read a Slice of Maps from a YAML Configuration File Using Go\'s Viper Library?

Tips for Reading a Slice of Maps with Golang Viper

In this article, we'll provide insights into reading a slice of maps using the popular Viper library in Go.

As mentioned, you're using Viper to manage configuration files, and you have a YAML configuration similar to the one shared. Your goal is to read the "group" option, which can contain multiple groups with their respective settings.

Understanding the Gotcha

When reading the "group" option using viper.GetStringMap(), you encountered an issue. This is because the "group" option is a slice of maps, not a single map. Viper cannot automatically infer this and returns an error.

The Solution: Custom Unmarshaling

To read a slice of maps, we recommend creating a custom config struct to represent your desired data structure. In your case, you can define structs for config, group, and target, as shown in the provided solution.

Once you've defined these structs, you can use viper.Unmarshal() to unmarshal the configuration into your custom struct. This will handle the slice of maps automatically and populate your struct accordingly.

Example Code:

type config struct {
    interval     int    `mapstructure:"interval"`
    statsdPrefix string `mapstructure:"statsd_prefix"`
    groups       []group `mapstructure:"group"`
}

type group struct {
    group         string `mapstructure:"group"`
    targetPrefix  string `mapstructure:"target_prefix"`
    targets       []target `mapstructure:"target"`
}

type target struct {
    target string   `mapstructure:"target"`
    hosts  []string `mapstructure:"hosts"`
}

var C config

err := viper.Unmarshal(&C)
if err != nil {
    panic(fmt.Errorf("unable to decode into struct, %v", err))
}

By following this approach, you can conveniently read your slice of maps using Viper.

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