How to Resolve the 'Package Without Selector' Error When Using Go Packages?

Getting a Grip on the "Package Without Selector" Enigma

When importing a package such as the versatile Viper configuration library, it's essential to understand the intent behind the "package without selector" error. By providing a bit of context, we can demystify this error and equip you with the knowledge to resolve it effectively.

Understanding the Issue

The error arises when attempting to directly use the package's name, such as "viper," without qualifying it with a specific exported identifier. Consider the following code snippet:

import "github.com/spf13/viper"

myConfig = NewMyConfig(&viper) // Error: use of package viper without selector

The Solution

To use the NewMyConfig function, which expects a *viper.Viper pointer, you have two options:

Option 1: Initialize a New Viper Instance

You can utilize the viper.New function to initialize a new viper.Viper instance:

vp := viper.New()
myConfig = NewMyConfig(vp)

Option 2: Leverage Global Functions

Alternatively, you can take advantage of the global functions exported by the viper package, which operate on a globally accessible viper.Viper instance:

myConfig = NewMyConfig(viper.GetViper())

This approach provides an alternative method to accessing and modifying viper configurations.

Understanding the Package Structure

Viper, like many other packages, employs an internal, unexported viper.Viper instance. Exported functions within the package serve as counterparts to the methods of the internal viper.Viper type.

By understanding this duality, you can choose to work with global functions or create your own Viper instances as needed.

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