github.com/morysky/viper@v1.8.0/README.md (about) 1 > ## Viper v2 feedback 2 > Viper is heading towards v2 and we would love to hear what _**you**_ would like to see in it. Share your thoughts here: https://forms.gle/R6faU74qPRPAzchZ9 3 > 4 > **Thank you!** 5 6 ![Viper](.github/logo.png?raw=true) 7 8 [![Mentioned in Awesome Go](https://awesome.re/mentioned-badge-flat.svg)](https://github.com/avelino/awesome-go#configuration) 9 [![run on repl.it](https://repl.it/badge/github/sagikazarmark/Viper-example)](https://repl.it/@sagikazarmark/Viper-example#main.go) 10 11 [![GitHub Workflow Status](https://img.shields.io/github/workflow/status/morysky/viper/CI?style=flat-square)](https://github.com/morysky/viper/actions?query=workflow%3ACI) 12 [![Join the chat at https://gitter.im/morysky/viper](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/morysky/viper?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) 13 [![Go Report Card](https://goreportcard.com/badge/github.com/morysky/viper?style=flat-square)](https://goreportcard.com/report/github.com/morysky/viper) 14 ![Go Version](https://img.shields.io/badge/go%20version-%3E=1.14-61CFDD.svg?style=flat-square) 15 [![PkgGoDev](https://pkg.go.dev/badge/mod/github.com/morysky/viper)](https://pkg.go.dev/mod/github.com/morysky/viper) 16 17 **Go configuration with fangs!** 18 19 Many Go projects are built using Viper including: 20 21 * [Hugo](http://gohugo.io) 22 * [EMC RexRay](http://rexray.readthedocs.org/en/stable/) 23 * [Imgur’s Incus](https://github.com/Imgur/incus) 24 * [Nanobox](https://github.com/nanobox-io/nanobox)/[Nanopack](https://github.com/nanopack) 25 * [Docker Notary](https://github.com/docker/Notary) 26 * [BloomApi](https://www.bloomapi.com/) 27 * [doctl](https://github.com/digitalocean/doctl) 28 * [Clairctl](https://github.com/jgsqware/clairctl) 29 * [Mercure](https://mercure.rocks) 30 31 32 ## Install 33 34 ```console 35 go get github.com/morysky/viper 36 ``` 37 38 39 ## What is Viper? 40 41 Viper is a complete configuration solution for Go applications including 12-Factor apps. It is designed 42 to work within an application, and can handle all types of configuration needs 43 and formats. It supports: 44 45 * setting defaults 46 * reading from JSON, TOML, YAML, HCL, envfile and Java properties config files 47 * live watching and re-reading of config files (optional) 48 * reading from environment variables 49 * reading from remote config systems (etcd or Consul), and watching changes 50 * reading from command line flags 51 * reading from buffer 52 * setting explicit values 53 54 Viper can be thought of as a registry for all of your applications configuration needs. 55 56 57 ## Why Viper? 58 59 When building a modern application, you don’t want to worry about 60 configuration file formats; you want to focus on building awesome software. 61 Viper is here to help with that. 62 63 Viper does the following for you: 64 65 1. Find, load, and unmarshal a configuration file in JSON, TOML, YAML, HCL, INI, envfile or Java properties formats. 66 2. Provide a mechanism to set default values for your different configuration options. 67 3. Provide a mechanism to set override values for options specified through command line flags. 68 4. Provide an alias system to easily rename parameters without breaking existing code. 69 5. Make it easy to tell the difference between when a user has provided a command line or config file which is the same as the default. 70 71 Viper uses the following precedence order. Each item takes precedence over the item below it: 72 73 * explicit call to `Set` 74 * flag 75 * env 76 * config 77 * key/value store 78 * default 79 80 **Important:** Viper configuration keys are case insensitive. 81 There are ongoing discussions about making that optional. 82 83 84 ## Putting Values into Viper 85 86 ### Establishing Defaults 87 88 A good configuration system will support default values. A default value is not 89 required for a key, but it’s useful in the event that a key hasn't been set via 90 config file, environment variable, remote configuration or flag. 91 92 Examples: 93 94 ```go 95 viper.SetDefault("ContentDir", "content") 96 viper.SetDefault("LayoutDir", "layouts") 97 viper.SetDefault("Taxonomies", map[string]string{"tag": "tags", "category": "categories"}) 98 ``` 99 100 ### Reading Config Files 101 102 Viper requires minimal configuration so it knows where to look for config files. 103 Viper supports JSON, TOML, YAML, HCL, INI, envfile and Java Properties files. Viper can search multiple paths, but 104 currently a single Viper instance only supports a single configuration file. 105 Viper does not default to any configuration search paths leaving defaults decision 106 to an application. 107 108 Here is an example of how to use Viper to search for and read a configuration file. 109 None of the specific paths are required, but at least one path should be provided 110 where a configuration file is expected. 111 112 ```go 113 viper.SetConfigName("config") // name of config file (without extension) 114 viper.SetConfigType("yaml") // REQUIRED if the config file does not have the extension in the name 115 viper.AddConfigPath("/etc/appname/") // path to look for the config file in 116 viper.AddConfigPath("$HOME/.appname") // call multiple times to add many search paths 117 viper.AddConfigPath(".") // optionally look for config in the working directory 118 err := viper.ReadInConfig() // Find and read the config file 119 if err != nil { // Handle errors reading the config file 120 panic(fmt.Errorf("Fatal error config file: %s \n", err)) 121 } 122 ``` 123 124 You can handle the specific case where no config file is found like this: 125 126 ```go 127 if err := viper.ReadInConfig(); err != nil { 128 if _, ok := err.(viper.ConfigFileNotFoundError); ok { 129 // Config file not found; ignore error if desired 130 } else { 131 // Config file was found but another error was produced 132 } 133 } 134 135 // Config file found and successfully parsed 136 ``` 137 138 *NOTE [since 1.6]:* You can also have a file without an extension and specify the format programmaticaly. For those configuration files that lie in the home of the user without any extension like `.bashrc` 139 140 ### Writing Config Files 141 142 Reading from config files is useful, but at times you want to store all modifications made at run time. 143 For that, a bunch of commands are available, each with its own purpose: 144 145 * WriteConfig - writes the current viper configuration to the predefined path, if exists. Errors if no predefined path. Will overwrite the current config file, if it exists. 146 * SafeWriteConfig - writes the current viper configuration to the predefined path. Errors if no predefined path. Will not overwrite the current config file, if it exists. 147 * WriteConfigAs - writes the current viper configuration to the given filepath. Will overwrite the given file, if it exists. 148 * SafeWriteConfigAs - writes the current viper configuration to the given filepath. Will not overwrite the given file, if it exists. 149 150 As a rule of the thumb, everything marked with safe won't overwrite any file, but just create if not existent, whilst the default behavior is to create or truncate. 151 152 A small examples section: 153 154 ```go 155 viper.WriteConfig() // writes current config to predefined path set by 'viper.AddConfigPath()' and 'viper.SetConfigName' 156 viper.SafeWriteConfig() 157 viper.WriteConfigAs("/path/to/my/.config") 158 viper.SafeWriteConfigAs("/path/to/my/.config") // will error since it has already been written 159 viper.SafeWriteConfigAs("/path/to/my/.other_config") 160 ``` 161 162 ### Watching and re-reading config files 163 164 Viper supports the ability to have your application live read a config file while running. 165 166 Gone are the days of needing to restart a server to have a config take effect, 167 viper powered applications can read an update to a config file while running and 168 not miss a beat. 169 170 Simply tell the viper instance to watchConfig. 171 Optionally you can provide a function for Viper to run each time a change occurs. 172 173 **Make sure you add all of the configPaths prior to calling `WatchConfig()`** 174 175 ```go 176 viper.WatchConfig() 177 viper.OnConfigChange(func(e fsnotify.Event) { 178 fmt.Println("Config file changed:", e.Name) 179 }) 180 ``` 181 182 ### Reading Config from io.Reader 183 184 Viper predefines many configuration sources such as files, environment 185 variables, flags, and remote K/V store, but you are not bound to them. You can 186 also implement your own required configuration source and feed it to viper. 187 188 ```go 189 viper.SetConfigType("yaml") // or viper.SetConfigType("YAML") 190 191 // any approach to require this configuration into your program. 192 var yamlExample = []byte(` 193 Hacker: true 194 name: steve 195 hobbies: 196 - skateboarding 197 - snowboarding 198 - go 199 clothing: 200 jacket: leather 201 trousers: denim 202 age: 35 203 eyes : brown 204 beard: true 205 `) 206 207 viper.ReadConfig(bytes.NewBuffer(yamlExample)) 208 209 viper.Get("name") // this would be "steve" 210 ``` 211 212 ### Setting Overrides 213 214 These could be from a command line flag, or from your own application logic. 215 216 ```go 217 viper.Set("Verbose", true) 218 viper.Set("LogFile", LogFile) 219 ``` 220 221 ### Registering and Using Aliases 222 223 Aliases permit a single value to be referenced by multiple keys 224 225 ```go 226 viper.RegisterAlias("loud", "Verbose") 227 228 viper.Set("verbose", true) // same result as next line 229 viper.Set("loud", true) // same result as prior line 230 231 viper.GetBool("loud") // true 232 viper.GetBool("verbose") // true 233 ``` 234 235 ### Working with Environment Variables 236 237 Viper has full support for environment variables. This enables 12 factor 238 applications out of the box. There are five methods that exist to aid working 239 with ENV: 240 241 * `AutomaticEnv()` 242 * `BindEnv(string...) : error` 243 * `SetEnvPrefix(string)` 244 * `SetEnvKeyReplacer(string...) *strings.Replacer` 245 * `AllowEmptyEnv(bool)` 246 247 _When working with ENV variables, it’s important to recognize that Viper 248 treats ENV variables as case sensitive._ 249 250 Viper provides a mechanism to try to ensure that ENV variables are unique. By 251 using `SetEnvPrefix`, you can tell Viper to use a prefix while reading from 252 the environment variables. Both `BindEnv` and `AutomaticEnv` will use this 253 prefix. 254 255 `BindEnv` takes one or more parameters. The first parameter is the key name, the 256 rest are the name of the environment variables to bind to this key. If more than 257 one are provided, they will take precedence in the specified order. The name of 258 the environment variable is case sensitive. If the ENV variable name is not provided, then 259 Viper will automatically assume that the ENV variable matches the following format: prefix + "_" + the key name in ALL CAPS. When you explicitly provide the ENV variable name (the second parameter), 260 it **does not** automatically add the prefix. For example if the second parameter is "id", 261 Viper will look for the ENV variable "ID". 262 263 One important thing to recognize when working with ENV variables is that the 264 value will be read each time it is accessed. Viper does not fix the value when 265 the `BindEnv` is called. 266 267 `AutomaticEnv` is a powerful helper especially when combined with 268 `SetEnvPrefix`. When called, Viper will check for an environment variable any 269 time a `viper.Get` request is made. It will apply the following rules. It will 270 check for an environment variable with a name matching the key uppercased and 271 prefixed with the `EnvPrefix` if set. 272 273 `SetEnvKeyReplacer` allows you to use a `strings.Replacer` object to rewrite Env 274 keys to an extent. This is useful if you want to use `-` or something in your 275 `Get()` calls, but want your environmental variables to use `_` delimiters. An 276 example of using it can be found in `viper_test.go`. 277 278 Alternatively, you can use `EnvKeyReplacer` with `NewWithOptions` factory function. 279 Unlike `SetEnvKeyReplacer`, it accepts a `StringReplacer` interface allowing you to write custom string replacing logic. 280 281 By default empty environment variables are considered unset and will fall back to 282 the next configuration source. To treat empty environment variables as set, use 283 the `AllowEmptyEnv` method. 284 285 #### Env example 286 287 ```go 288 SetEnvPrefix("spf") // will be uppercased automatically 289 BindEnv("id") 290 291 os.Setenv("SPF_ID", "13") // typically done outside of the app 292 293 id := Get("id") // 13 294 ``` 295 296 ### Working with Flags 297 298 Viper has the ability to bind to flags. Specifically, Viper supports `Pflags` 299 as used in the [Cobra](https://github.com/spf13/cobra) library. 300 301 Like `BindEnv`, the value is not set when the binding method is called, but when 302 it is accessed. This means you can bind as early as you want, even in an 303 `init()` function. 304 305 For individual flags, the `BindPFlag()` method provides this functionality. 306 307 Example: 308 309 ```go 310 serverCmd.Flags().Int("port", 1138, "Port to run Application server on") 311 viper.BindPFlag("port", serverCmd.Flags().Lookup("port")) 312 ``` 313 314 You can also bind an existing set of pflags (pflag.FlagSet): 315 316 Example: 317 318 ```go 319 pflag.Int("flagname", 1234, "help message for flagname") 320 321 pflag.Parse() 322 viper.BindPFlags(pflag.CommandLine) 323 324 i := viper.GetInt("flagname") // retrieve values from viper instead of pflag 325 ``` 326 327 The use of [pflag](https://github.com/spf13/pflag/) in Viper does not preclude 328 the use of other packages that use the [flag](https://golang.org/pkg/flag/) 329 package from the standard library. The pflag package can handle the flags 330 defined for the flag package by importing these flags. This is accomplished 331 by a calling a convenience function provided by the pflag package called 332 AddGoFlagSet(). 333 334 Example: 335 336 ```go 337 package main 338 339 import ( 340 "flag" 341 "github.com/spf13/pflag" 342 ) 343 344 func main() { 345 346 // using standard library "flag" package 347 flag.Int("flagname", 1234, "help message for flagname") 348 349 pflag.CommandLine.AddGoFlagSet(flag.CommandLine) 350 pflag.Parse() 351 viper.BindPFlags(pflag.CommandLine) 352 353 i := viper.GetInt("flagname") // retrieve value from viper 354 355 ... 356 } 357 ``` 358 359 #### Flag interfaces 360 361 Viper provides two Go interfaces to bind other flag systems if you don’t use `Pflags`. 362 363 `FlagValue` represents a single flag. This is a very simple example on how to implement this interface: 364 365 ```go 366 type myFlag struct {} 367 func (f myFlag) HasChanged() bool { return false } 368 func (f myFlag) Name() string { return "my-flag-name" } 369 func (f myFlag) ValueString() string { return "my-flag-value" } 370 func (f myFlag) ValueType() string { return "string" } 371 ``` 372 373 Once your flag implements this interface, you can simply tell Viper to bind it: 374 375 ```go 376 viper.BindFlagValue("my-flag-name", myFlag{}) 377 ``` 378 379 `FlagValueSet` represents a group of flags. This is a very simple example on how to implement this interface: 380 381 ```go 382 type myFlagSet struct { 383 flags []myFlag 384 } 385 386 func (f myFlagSet) VisitAll(fn func(FlagValue)) { 387 for _, flag := range flags { 388 fn(flag) 389 } 390 } 391 ``` 392 393 Once your flag set implements this interface, you can simply tell Viper to bind it: 394 395 ```go 396 fSet := myFlagSet{ 397 flags: []myFlag{myFlag{}, myFlag{}}, 398 } 399 viper.BindFlagValues("my-flags", fSet) 400 ``` 401 402 ### Remote Key/Value Store Support 403 404 To enable remote support in Viper, do a blank import of the `viper/remote` 405 package: 406 407 `import _ "github.com/morysky/viper/remote"` 408 409 Viper will read a config string (as JSON, TOML, YAML, HCL or envfile) retrieved from a path 410 in a Key/Value store such as etcd or Consul. These values take precedence over 411 default values, but are overridden by configuration values retrieved from disk, 412 flags, or environment variables. 413 414 Viper uses [crypt](https://github.com/bketelsen/crypt) to retrieve 415 configuration from the K/V store, which means that you can store your 416 configuration values encrypted and have them automatically decrypted if you have 417 the correct gpg keyring. Encryption is optional. 418 419 You can use remote configuration in conjunction with local configuration, or 420 independently of it. 421 422 `crypt` has a command-line helper that you can use to put configurations in your 423 K/V store. `crypt` defaults to etcd on http://127.0.0.1:4001. 424 425 ```bash 426 $ go get github.com/bketelsen/crypt/bin/crypt 427 $ crypt set -plaintext /config/hugo.json /Users/hugo/settings/config.json 428 ``` 429 430 Confirm that your value was set: 431 432 ```bash 433 $ crypt get -plaintext /config/hugo.json 434 ``` 435 436 See the `crypt` documentation for examples of how to set encrypted values, or 437 how to use Consul. 438 439 ### Remote Key/Value Store Example - Unencrypted 440 441 #### etcd 442 ```go 443 viper.AddRemoteProvider("etcd", "http://127.0.0.1:4001","/config/hugo.json") 444 viper.SetConfigType("json") // because there is no file extension in a stream of bytes, supported extensions are "json", "toml", "yaml", "yml", "properties", "props", "prop", "env", "dotenv" 445 err := viper.ReadRemoteConfig() 446 ``` 447 448 #### Consul 449 You need to set a key to Consul key/value storage with JSON value containing your desired config. 450 For example, create a Consul key/value store key `MY_CONSUL_KEY` with value: 451 452 ```json 453 { 454 "port": 8080, 455 "hostname": "myhostname.com" 456 } 457 ``` 458 459 ```go 460 viper.AddRemoteProvider("consul", "localhost:8500", "MY_CONSUL_KEY") 461 viper.SetConfigType("json") // Need to explicitly set this to json 462 err := viper.ReadRemoteConfig() 463 464 fmt.Println(viper.Get("port")) // 8080 465 fmt.Println(viper.Get("hostname")) // myhostname.com 466 ``` 467 468 #### Firestore 469 470 ```go 471 viper.AddRemoteProvider("firestore", "google-cloud-project-id", "collection/document") 472 viper.SetConfigType("json") // Config's format: "json", "toml", "yaml", "yml" 473 err := viper.ReadRemoteConfig() 474 ``` 475 476 Of course, you're allowed to use `SecureRemoteProvider` also 477 478 ### Remote Key/Value Store Example - Encrypted 479 480 ```go 481 viper.AddSecureRemoteProvider("etcd","http://127.0.0.1:4001","/config/hugo.json","/etc/secrets/mykeyring.gpg") 482 viper.SetConfigType("json") // because there is no file extension in a stream of bytes, supported extensions are "json", "toml", "yaml", "yml", "properties", "props", "prop", "env", "dotenv" 483 err := viper.ReadRemoteConfig() 484 ``` 485 486 ### Watching Changes in etcd - Unencrypted 487 488 ```go 489 // alternatively, you can create a new viper instance. 490 var runtime_viper = viper.New() 491 492 runtime_viper.AddRemoteProvider("etcd", "http://127.0.0.1:4001", "/config/hugo.yml") 493 runtime_viper.SetConfigType("yaml") // because there is no file extension in a stream of bytes, supported extensions are "json", "toml", "yaml", "yml", "properties", "props", "prop", "env", "dotenv" 494 495 // read from remote config the first time. 496 err := runtime_viper.ReadRemoteConfig() 497 498 // unmarshal config 499 runtime_viper.Unmarshal(&runtime_conf) 500 501 // open a goroutine to watch remote changes forever 502 go func(){ 503 for { 504 time.Sleep(time.Second * 5) // delay after each request 505 506 // currently, only tested with etcd support 507 err := runtime_viper.WatchRemoteConfig() 508 if err != nil { 509 log.Errorf("unable to read remote config: %v", err) 510 continue 511 } 512 513 // unmarshal new config into our runtime config struct. you can also use channel 514 // to implement a signal to notify the system of the changes 515 runtime_viper.Unmarshal(&runtime_conf) 516 } 517 }() 518 ``` 519 520 ## Getting Values From Viper 521 522 In Viper, there are a few ways to get a value depending on the value’s type. 523 The following functions and methods exist: 524 525 * `Get(key string) : interface{}` 526 * `GetBool(key string) : bool` 527 * `GetFloat64(key string) : float64` 528 * `GetInt(key string) : int` 529 * `GetIntSlice(key string) : []int` 530 * `GetString(key string) : string` 531 * `GetStringMap(key string) : map[string]interface{}` 532 * `GetStringMapString(key string) : map[string]string` 533 * `GetStringSlice(key string) : []string` 534 * `GetTime(key string) : time.Time` 535 * `GetDuration(key string) : time.Duration` 536 * `IsSet(key string) : bool` 537 * `AllSettings() : map[string]interface{}` 538 539 One important thing to recognize is that each Get function will return a zero 540 value if it’s not found. To check if a given key exists, the `IsSet()` method 541 has been provided. 542 543 Example: 544 ```go 545 viper.GetString("logfile") // case-insensitive Setting & Getting 546 if viper.GetBool("verbose") { 547 fmt.Println("verbose enabled") 548 } 549 ``` 550 ### Accessing nested keys 551 552 The accessor methods also accept formatted paths to deeply nested keys. For 553 example, if the following JSON file is loaded: 554 555 ```json 556 { 557 "host": { 558 "address": "localhost", 559 "port": 5799 560 }, 561 "datastore": { 562 "metric": { 563 "host": "127.0.0.1", 564 "port": 3099 565 }, 566 "warehouse": { 567 "host": "198.0.0.1", 568 "port": 2112 569 } 570 } 571 } 572 573 ``` 574 575 Viper can access a nested field by passing a `.` delimited path of keys: 576 577 ```go 578 GetString("datastore.metric.host") // (returns "127.0.0.1") 579 ``` 580 581 This obeys the precedence rules established above; the search for the path 582 will cascade through the remaining configuration registries until found. 583 584 For example, given this configuration file, both `datastore.metric.host` and 585 `datastore.metric.port` are already defined (and may be overridden). If in addition 586 `datastore.metric.protocol` was defined in the defaults, Viper would also find it. 587 588 However, if `datastore.metric` was overridden (by a flag, an environment variable, 589 the `Set()` method, …) with an immediate value, then all sub-keys of 590 `datastore.metric` become undefined, they are “shadowed” by the higher-priority 591 configuration level. 592 593 Viper can access array indices by using numbers in the path. For example: 594 595 ```json 596 { 597 "host": { 598 "address": "localhost", 599 "ports": [ 600 5799, 601 6029 602 ] 603 }, 604 "datastore": { 605 "metric": { 606 "host": "127.0.0.1", 607 "port": 3099 608 }, 609 "warehouse": { 610 "host": "198.0.0.1", 611 "port": 2112 612 } 613 } 614 } 615 616 GetInt("host.ports.1") // returns 6029 617 618 ``` 619 620 Lastly, if there exists a key that matches the delimited key path, its value 621 will be returned instead. E.g. 622 623 ```json 624 { 625 "datastore.metric.host": "0.0.0.0", 626 "host": { 627 "address": "localhost", 628 "port": 5799 629 }, 630 "datastore": { 631 "metric": { 632 "host": "127.0.0.1", 633 "port": 3099 634 }, 635 "warehouse": { 636 "host": "198.0.0.1", 637 "port": 2112 638 } 639 } 640 } 641 642 GetString("datastore.metric.host") // returns "0.0.0.0" 643 ``` 644 645 ### Extracting a sub-tree 646 647 When developing reusable modules, it's often useful to extract a subset of the configuration 648 and pass it to a module. This way the module can be instantiated more than once, with different configurations. 649 650 For example, an application might use multiple different cache stores for different purposes: 651 652 ```yaml 653 cache: 654 cache1: 655 max-items: 100 656 item-size: 64 657 cache2: 658 max-items: 200 659 item-size: 80 660 ``` 661 662 We could pass the cache name to a module (eg. `NewCache("cache1")`), 663 but it would require weird concatenation for accessing config keys and would be less separated from the global config. 664 665 So instead of doing that let's pass a Viper instance to the constructor that represents a subset of the configuration: 666 667 ```go 668 cache1Config := viper.Sub("cache.cache1") 669 if cache1Config == nil { // Sub returns nil if the key cannot be found 670 panic("cache configuration not found") 671 } 672 673 cache1 := NewCache(cache1Config) 674 ``` 675 676 **Note:** Always check the return value of `Sub`. It returns `nil` if a key cannot be found. 677 678 Internally, the `NewCache` function can address `max-items` and `item-size` keys directly: 679 680 ```go 681 func NewCache(v *Viper) *Cache { 682 return &Cache{ 683 MaxItems: v.GetInt("max-items"), 684 ItemSize: v.GetInt("item-size"), 685 } 686 } 687 ``` 688 689 The resulting code is easy to test, since it's decoupled from the main config structure, 690 and easier to reuse (for the same reason). 691 692 693 ### Unmarshaling 694 695 You also have the option of Unmarshaling all or a specific value to a struct, map, 696 etc. 697 698 There are two methods to do this: 699 700 * `Unmarshal(rawVal interface{}) : error` 701 * `UnmarshalKey(key string, rawVal interface{}) : error` 702 703 Example: 704 705 ```go 706 type config struct { 707 Port int 708 Name string 709 PathMap string `mapstructure:"path_map"` 710 } 711 712 var C config 713 714 err := viper.Unmarshal(&C) 715 if err != nil { 716 t.Fatalf("unable to decode into struct, %v", err) 717 } 718 ``` 719 720 If you want to unmarshal configuration where the keys themselves contain dot (the default key delimiter), 721 you have to change the delimiter: 722 723 ```go 724 v := viper.NewWithOptions(viper.KeyDelimiter("::")) 725 726 v.SetDefault("chart::values", map[string]interface{}{ 727 "ingress": map[string]interface{}{ 728 "annotations": map[string]interface{}{ 729 "traefik.frontend.rule.type": "PathPrefix", 730 "traefik.ingress.kubernetes.io/ssl-redirect": "true", 731 }, 732 }, 733 }) 734 735 type config struct { 736 Chart struct{ 737 Values map[string]interface{} 738 } 739 } 740 741 var C config 742 743 v.Unmarshal(&C) 744 ``` 745 746 Viper also supports unmarshaling into embedded structs: 747 748 ```go 749 /* 750 Example config: 751 752 module: 753 enabled: true 754 token: 89h3f98hbwf987h3f98wenf89ehf 755 */ 756 type config struct { 757 Module struct { 758 Enabled bool 759 760 moduleConfig `mapstructure:",squash"` 761 } 762 } 763 764 // moduleConfig could be in a module specific package 765 type moduleConfig struct { 766 Token string 767 } 768 769 var C config 770 771 err := viper.Unmarshal(&C) 772 if err != nil { 773 t.Fatalf("unable to decode into struct, %v", err) 774 } 775 ``` 776 777 Viper uses [github.com/mitchellh/mapstructure](https://github.com/mitchellh/mapstructure) under the hood for unmarshaling values which uses `mapstructure` tags by default. 778 779 ### Marshalling to string 780 781 You may need to marshal all the settings held in viper into a string rather than write them to a file. 782 You can use your favorite format's marshaller with the config returned by `AllSettings()`. 783 784 ```go 785 import ( 786 yaml "gopkg.in/yaml.v2" 787 // ... 788 ) 789 790 func yamlStringSettings() string { 791 c := viper.AllSettings() 792 bs, err := yaml.Marshal(c) 793 if err != nil { 794 log.Fatalf("unable to marshal config to YAML: %v", err) 795 } 796 return string(bs) 797 } 798 ``` 799 800 ## Viper or Vipers? 801 802 Viper comes ready to use out of the box. There is no configuration or 803 initialization needed to begin using Viper. Since most applications will want 804 to use a single central repository for their configuration, the viper package 805 provides this. It is similar to a singleton. 806 807 In all of the examples above, they demonstrate using viper in its singleton 808 style approach. 809 810 ### Working with multiple vipers 811 812 You can also create many different vipers for use in your application. Each will 813 have its own unique set of configurations and values. Each can read from a 814 different config file, key value store, etc. All of the functions that viper 815 package supports are mirrored as methods on a viper. 816 817 Example: 818 819 ```go 820 x := viper.New() 821 y := viper.New() 822 823 x.SetDefault("ContentDir", "content") 824 y.SetDefault("ContentDir", "foobar") 825 826 //... 827 ``` 828 829 When working with multiple vipers, it is up to the user to keep track of the 830 different vipers. 831 832 ## Q & A 833 834 ### Why is it called “Viper”? 835 836 A: Viper is designed to be a [companion](http://en.wikipedia.org/wiki/Viper_(G.I._Joe)) 837 to [Cobra](https://github.com/spf13/cobra). While both can operate completely 838 independently, together they make a powerful pair to handle much of your 839 application foundation needs. 840 841 ### Why is it called “Cobra”? 842 843 Is there a better name for a [commander](http://en.wikipedia.org/wiki/Cobra_Commander)? 844 845 ### Does Viper support case sensitive keys? 846 847 **tl;dr:** No. 848 849 Viper merges configuration from various sources, many of which are either case insensitive or uses different casing than the rest of the sources (eg. env vars). 850 In order to provide the best experience when using multiple sources, the decision has been made to make all keys case insensitive. 851 852 There has been several attempts to implement case sensitivity, but unfortunately it's not that trivial. We might take a stab at implementing it in [Viper v2](https://github.com/morysky/viper/issues/772), but despite the initial noise, it does not seem to be requested that much. 853 854 You can vote for case sensitivity by filling out this feedback form: https://forms.gle/R6faU74qPRPAzchZ9 855