Gocfg

Gocfg is an interpolate library for a configuration. It reads from files (yml, toml, json, conf, ...) and sets the corresponding parameter values on a struct. The cool part of this library is that this reading process is interpolated, in other words this means that you could use variables to search for environment variables and define default values if they don’t exist, all in the file. eg:

some_key: "test"
another_key: 1234
sub_object:
  something: "a"
  something_else: 1234
  something_else_with_interpolation: "{SOMETHING_ELSE_WITH_INTERPOLATION:3432.8}"
last_key: "{LAST_KEY:default value}"
last_key_with_number: "{LAST_KEY_WITH_NUMBER:54}"

As you can see the if you set the value as "{ENVIRONMENT_VARIABLE:default_value}" or only "{ENVIRONMENT_VARIABLE}" if the variable doesn't have a default value.

Is important to remember that, if you want to know when an environment variable is missing to not start your application you need to configure the field with the required tag and not set a default. Doing that the load will return an error.

How is the code part?

On your code you must have a struct to be mapped by the lib like that:

var SomeStruct = struct {
    SomeKey    string `cfg:"some_key"`
    AnotherKey int    `cfg:"another_key"`
    SubObject  struct {
        SomeThing                      string  `cfg:"something"`
        SomethingElse                  int     `cfg:"something_else"`
        SomethingElseWithInterpolation float64 `cfg:"something_else_with_interpolation"`
    } `cfg:"sub_object"`
    LastKey           string `cfg:"last_key"`
    LastKeyWithNumber uint   `cfg:"last_key_with_number"`
}{}

Or if you want a more organized way of segregating your nested structures into different independent types:

type SomeStruct struct {
    SomeKey           string
    AnotherKey        int
    SubObject         SubObjectType
    LastKey           string
    LastKeyWithNumber uint
}

type SubObjectType struct {
    SomeThing                      string
    SomethingElse                  int
    SomethingElseWithInterpolation float64
}

The "cfg" tag, like the json tag, acts as an alias when binding the keys in the file with your struct's parameters. They are helpful but not obligatory.

Required

Required subtag is meant to signalize for the lib when a field that doesn’t have a default value, and your application expects some value to be set.

type Example struct {
    First  float64 `cfg:"required"`
    Second bool    `cfg:"SECOND,required"`
}

Starting the load process

To load the configurations you just need to use the function load from the lib. e.g.:

err := gocfg.Load(&variable, gocfg.YAML, "/your/file/location.yml")

If you want to, you don't need to pass a file path. The lib will set by default an application.{your selected file type} on your current directory The file types are selected as integers, but the library has an iota enum that helps you to easily set the load. Currently, we have:

• YAML;
• JSON;
• ENV (this means fulls environment variables, not "dotenv");
• TOML;