Introduction to Viper in Go and Golang

In Go, there are a lot of packages to deal with software configuration. The viper bundle is hottest amongst them in offering a whole configuration resolution of an software. It helps quite a few configuration file codecs corresponding to JSON, YAML, TOML, HCL and Java properties format. This programming tutorial introduces Golang’s viper bundle with Go code examples.

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What’s the viper Library in Go and Golang?

As talked about, viper is a bundle that gives a whole configuration resolution in a Go venture. Managing and sustaining configuration for an enormous and sophisticated software – corresponding to constructing a server software or another software which relies upon quite a bit on person manipulation of configurations – will not be a simple job. Furthermore, fashionable purposes are constructed to deploy in various kinds of environments, corresponding to in Docker, cloud infrastructures, and so forth. Consequently, with a purpose to keep consistency throughout deployment, purposes needs to be constructed to be open from little to excessive configurability. An exterior help that helps on this respect will not be solely a respite, but in addition very a lot welcome for the builders concerned in constructing such an answer.

The viper library, on this respect, can totally change the flag bundle, which offers provisions for creating UNIX methods, corresponding to command line utilities. In keeping with the viper documentation, viper, aside from being a whole configuration resolution for Go purposes, additionally helps 12-Issue apps. 12-Issue app is a technique for constructing software-as-a-service (SAAS) purposes. Launched by Heroku, this system leverages portability, declarative codecs, and automation that makes purposes extra resilient to the adaptive wants of the altering setting of software program deployment.

Learn: How you can Use the flag Package deal in Go

What Does the viper Library Help in Go?

In keeping with the viper documentation, it helps the next in Go purposes:

  • Studying JSON, TOML, YAML, HCL, envfile and Java properties config recordsdata. Most configuration info of an software is written on this format. Viper helps most of them.
  • Organising default configurations
  • Studying setting variables
  • Studying distant configuration methods
  • Studying from command line flags
  • Studying from buffer
  • Setting express values

How you can Set up viper in Go

The steps to put in viper are just like putting in another bundle in Go. As soon as a Go software venture has been arrange correctly with the required module file utilizing the go mod init command, a go.mod file might be created. This file maintains the record of packages used within the present venture. Simply kind: go get to put in the viper bundle. Observe {that a} new record of packages associated to the viper bundle might be added within the go.mod file.

Go viper Code Instance

Suppose we wish to get the values of the widespread Working System setting variable known as PATH. Builders might accomplish that utilizing the next Go code instance:

bundle most important

import (

func most important() {
val := viper.Get("PATH")
fmt.Println("PATH:", val)

Word that, within the perform most important(), we used viper.BindEnv to bind a viper key to the setting variable known as PATH. It’s case delicate, which means, as the bottom line is supplied, it would use the setting key that matches the important thing in uppercase if given in uppercase. Since, BindEnv can take multiple argument, every will signify setting variable names that bind to this key and might be taken within the specified order.

The viper.Get perform is used to retrieve any worth given the important thing to make use of. Right here, we use it to retrieve the worth within the Working System’s PATH setting variable. Observe within the following Golang code instance that we can’t solely retrieve values from the setting variable, but in addition set them as required:

eval := viper.Get("GOMAXPROCS")
fmt.Println("GOMAXPROCS:", eval) 

viper.Set("GOMAXPROCS", 20)
eval = viper.Get("GOMAXPROCS")
fmt.Println("GOMAXPROCS:", eval)

We are able to additionally set new setting variables by Go code, topic to the Working System’s permission, in fact:

cval := viper.Get("MYVARIABLE")
if cval == nil {
	fmt.Println("MYVARIABLE couldn't be outlined.")

Word that the flag bundle doesn’t supply such flexibility, however the os bundle in the usual library provides some. Nonetheless, the viper bundle makes it a lot simpler to make use of.

Learn: The Finest Instruments for Distant Builders

How you can Learn JSON Configuration Information in Go along with viper

Generally, configuration recordsdata are written in a separate configuration file in one of many many alternative obtainable codecs, corresponding to JSON. The viper bundle is totally geared up to learn and extract info saved there. Right here is a few fast instance code of easy methods to learn a JSON configuration file in Go.

Let the JSON config file: testJSONConfig.json be as follows:

"init-param": {
"installAt": "Philadelphia, PA",
"adminEmail": "[email protected]",
"staticPath": "/content material/static"
"taglib": {

The Go code snippet to learn the JSON file is as follows:

fmt.Printf("Utilizing config: %sn", viper.ConfigFileUsed())

if viper.IsSet("init-param.installAt") {
fmt.Println("init-param.installAt:", viper.Get("init-param.installAt"))
} else {
fmt.Println(" init-param.installAt not set.")
if viper.IsSet("init-param.staticPath") {
fmt.Println("init-param.staticPath:", viper.Get("init-param.staticPath"))
} else {
fmt.Println(" init-param.staticPath will not be set.")

Working with different fashionable file codecs, corresponding to YAML, TOML, HCL, and so forth, utilizing viper is kind of related.

Unmarshalling By way of viper in Go

Apparently, viper additionally offers the function of unmarshalling of values from configuration recordsdata to Go sorts corresponding to struct, map, and so forth. Here’s a fast instance of easy methods to unmarshal with viper in Go:

kind configType struct {
InstallAt string
Model string
StaticPath string

var config configType

err := viper.Unmarshal(&config)
if err != nil {
fmt.Println("Unmarshalling failed!")

Word that the marshalling options are sometimes supplied by the bundle of the file format we wish to marshall. For instance, if we wish to marshall a Go kind right into a YAML file, then the YAML Go bundle will present the marshalling function.

Closing Ideas on the Go Library viper

This has been a fast overview of the viper bundle, with a glimpse of its use in Go. Extra detailed info may be obtained from the viper documentation itself. Perceive that viper, in spite of everything, is a software for use in keeping with the requirement of the software program being developed. It helps many wonderful options associated to storing and retrieving configuration info sought by programmers in fashionable software growth.

Each functionality of viper might not be required in the mean time, however that ought to not cease one from utilizing a few of its options. Utilizing judiciously is the important thing. For instance, it’s higher to make use of configuration recordsdata as an alternative of utilizing command line utilities to provide too many configuration parameters and flags. On this scenario, the options supplied by the viper bundle may be fairly useful.

Learn extra Go programming tutorials and Golang growth suggestions.

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