A simple config manager for Go applications.

Use the following:

go get -u github.com/shivanshkc/confetti/v2

Confetti only has a few, but well implemented set of features. It makes it really easy to use and understand.
If your application fits the following use-case, Confetti is the best config manager you can get.

1. The configs have to be loaded/unmarshalled into a struct.
2. The configs are loaded once at application startup and do not change for the entire runtime of the application.
3. The configs are loaded either from the environment or command-line flags (No JSON/YAML files or remote servers).

If your application agrees with the above restrictions, you can enjoy the following features of Confetti:

1. Concise syntax using struct tags

   package main
   
   type Configs struct {
       Port string `def:"8080" env:"PORT" arg:"port"`
   }

   This is all you need to make a struct usable with Confetti. Use the following code to load the configs:

   import (
       "fmt"
   
       "github.com/shivanshkc/confetti/v2"
   )   
   
   func main() {
       loader := confetti.NewDefLoader()
   
       configs := &Configs{}
       if err := loader.Load(configs); err != nil {
           panic(err)
       }
   
       fmt.Println("Configs:", configs)
   }

   Here, as you may have guessed:
   a. The Port config has the default value of 8080.
   b. If the environment variable PORT is provided, it will override the default value.
   c. If the -port or --port flag is provided, it will override both the default value and the environment variable.

2. Generates documentation for your application

   If you use the code in the last point, and execute go run main.go -h, you will see the following on your console:

   Usage of configs:
   -port value
           Doc: not provided
           Default: 8080
           Environment: PORT
   panic: failed to parse flags: flag: help requested
   

   Confetti auto-generates this help documentation for your application using Go's flag package.
   In the output above, notice the Doc: not provided line. This is because we did not provide any doc on the Port config. It can be provided as follows:

   type Configs struct {
       Port string `def:"8080" env:"PORT" arg:"port,HTTP server port"`
   }

   Now, the output will read:

   Usage of configs:
   -port value
       Doc: HTTP server port
       Default: 8080
       Environment: PORT
   panic: failed to parse flags: flag: help requested
   

   Next, you must be getting annoyed by the panic message at the bottom. This is because Go's flag package returns an error when a -h or -help flag is provided. To get rid of this, use the following:

   import (
       "errors"
       "fmt"
   
       "github.com/shivanshkc/confetti/v2"   
   )
   
   func main() {
       loader := confetti.NewDefLoader()
   
       configs := &Configs{}
       if err := loader.Load(configs); err != nil {
           if errors.Is(err, flag.ErrHelp) {
   	        return
           }
           panic(err)
       }
   
       fmt.Println("Configs:", configs)
   }

3. Nested structs

   Confetti is built to handle nested structs. Just make sure that the flag names for all fields are always different, otherwise you'll get a panic.

   type Configs struct {
       HTTP struct {
           Port string `def:"8080" env:"HTTP_PORT" arg:"http-port"`
       }
   
       GRPC struct {
           Port string `def:"7070" env:"GRPC_PORT" arg:"grpc-port"`
       }
   }

   The above struct is a completely valid Confetti target.

4. Automatic type assertions

   Confetti is built to handle all types of configs, and not just strings. Consider the following example:

   type Configs struct {
       CORS struct {
           TrustedOrigins []string `def:"[\"google.com\"]" env:"TRUSTED_ORIGINS" arg:"trusted-origins"`
       }
   
       Pagination struct {
           DefaultLimit int `def:"100" env:"DEFAULT_LIMIT" arg:"default-limit"`
       }
   
       RedisDetails map[string]string `def:"{}" env:"REDIS_DETAILS" arg:"redis-details"`
   }

   This struct is also a valid Confetti target. Just make sure that the value of the environment variable or flag is a valid JSON string, otherwise Confetti will give you an error.

Confetti exposes a NewLoader function and a NewDefLoader function (as used in the examples above).
The NewDefLoader uses the default options, but users can provide their own options by using the NewLoader function.
Here is the explanation of all available options: