config

Meta-Viper is a wrapper over viper, it uses a Go tagged struct to:

1. Initialize viper's configuration.

2. Load application configuration on that same struct.

You can find examples at ./examples or in this article: https://carlosvin.github.io/posts/create-cmd-tool-golang.

Usage {#_usage}

Define the struct holding your application config

Meta-Viper will try to load the configuration in that struct from configuration files, environment variables or flags.

Example.

package main

import (
    "fmt"
    "os"

    config "github.com/carlosvin/meta-viper"
)

type appConfig struct {
    Host      string `cfg_name:"host" cfg_desc:"Server host"`
    Port      int    `cfg_name:"port" cfg_desc:"Server port"`
    SearchAPI string `cfg_name:"apis.search" cfg_desc:"Search API endpoint"`
}

func main() {
    cfg := &appConfig{ 
        Host: "localhost",
        Port: 6000,
        SearchAPI: "https://google.es",
    }

    _, err := config.New(cfg, os.Args) 
    if err != nil {
        panic(err)
    }
    log.Printf("Loaded Configuration %v...", cfg)
}

• We instantiate the declared struct. As you can see you can optionally specify default values.

• It loads the configuration in the passed struct cfg. The os.Args are required to parse the application flags.

Let’s focus on one application configuration attribute to explain the example. Meta-Viper will allow you to load the config into Host structure attribute in 3 different ways:

Using flags.

./your-program --host=my.host

Using environment variables.

HOST=my.host ./your-program

Loading the data from a file in json, yaml or toml format.

./your-program --config=qa 

• Following the qa configuration file content

qa.json.

{
    "host": "qa.host",
    "port": 8000,
    "apis": {
        "search": "https://search.api/"
    }
}

Tags {#_tags}

cfg_name

Required tag to specify the configuration parameter name.

cfg_description

Optional tag to describe how to use the configuration parameter.