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Introduction to Viper in Go and Golang


In Go, there are lots of packages to deal with software configuration. The viper package deal is hottest amongst them in offering an entire configuration answer 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 package deal with Go code examples.

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What’s the viper Library in Go and Golang?

As talked about, viper is a package deal that gives an entire configuration answer in a Go venture. Managing and sustaining configuration for a giant and sophisticated software – corresponding to constructing a server software or every other software which relies upon lots on consumer manipulation of configurations – shouldn’t be a straightforward activity. Furthermore, fashionable functions are constructed to deploy in several types of environments, corresponding to in Docker, cloud infrastructures, and so forth. Consequently, as a way to keep consistency throughout deployment, functions needs to be constructed to be open from little to excessive configurability. An exterior help that helps on this respect shouldn’t 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 fully change the flag package deal, which gives provisions for growing UNIX methods, corresponding to command line utilities. In response to the viper documentation, viper, aside from being an entire configuration answer for Go functions, additionally helps 12-Issue apps. 12-Issue app is a technique for constructing software-as-a-service (SAAS) functions. Launched by Heroku, this system leverages portability, declarative codecs, and automation that makes functions extra resilient to the adaptive wants of the altering surroundings of software program deployment.

Learn: Find out how to Use the flag Package deal in Go

What Does the viper Library Assist in Go?

In response to the viper documentation, it helps the next in Go functions:

  • 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.
  • Establishing default configurations
  • Studying surroundings variables
  • Studying distant configuration methods
  • Studying from command line flags
  • Studying from buffer
  • Setting express values

Find out how to Set up viper in Go

The steps to put in viper are much like putting in every other package deal 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 checklist of packages used within the present venture. Simply kind: go get to put in the viper package deal. Observe {that a} new checklist of packages associated to the viper package deal might be added within the go.mod file.

Go viper Code Instance

Suppose we wish to get the values of the frequent Working System surroundings variable known as PATH. Builders could achieve this utilizing the next Go code instance:

package deal important

import (

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

Notice that, within the perform important(), we used viper.BindEnv to bind a viper key to the surroundings variable known as PATH. It’s case delicate, which means, as the secret’s supplied, it’s going to use the surroundings key that matches the important thing in uppercase if given in uppercase. Since, BindEnv can take a couple of argument, every will characterize surroundings 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 surroundings variable. Observe within the following Golang code instance that we cannot solely retrieve values from the surroundings 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 will additionally set new surroundings variables by means of Go code, topic to the Working System’s permission, after all:

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

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

Learn: The Finest Instruments for Distant Builders

Find out how to Learn JSON Configuration Information in Go together with viper

Typically, configuration recordsdata are written in a separate configuration file in one of many many various obtainable codecs, corresponding to JSON. The viper package deal is totally geared up to learn and extract info saved there. Right here is a few fast instance code of 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 shouldn't be set.")

Working with different in style 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 gives the characteristic of unmarshalling of values from configuration recordsdata to Go sorts corresponding to struct, map, and so forth. Here’s a fast instance of 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!")

Notice that the marshalling options are usually supplied by the package deal 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 package deal will present the marshalling characteristic.

Remaining Ideas on the Go Library viper

This has been a fast overview of the viper package deal, with a glimpse of its use in Go. Extra detailed info might be obtained from the viper documentation itself. Perceive that viper, in any case, is a device 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 is probably not required for the time being, 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 produce too many configuration parameters and flags. On this state of affairs, the options supplied by the viper package deal might be fairly useful.

Learn extra Go programming tutorials and Golang growth suggestions.



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