confunc provides a functional approach to configure an application. With confunc, each configuraion value can be defined as a function, providing a dynamic value rather than a static one that is assigned once the application starts up.

Example:

// declare your configuration value
maxNumberOfOpenConnections := confunc.From(confunc.Env()).Int("MAX_OPEN_CONNECTIONS")
...
// when you need to access the value
if connectionCount < maxNumberOfOpenConnections() {
    // do your thing
}

Source is where the configuration is retrieved. It is defined by the Source interface where a string value is returned for a specified key. Once it is passed to confunc.From() function; a struct that can return configuration functions is created. Available sources are:

• Env() : retrieves Environment Variables
• Map(map[string]string) : retrieves configuration from a map
• cfconsul.Source(*api.Config) : retrieves configuration from consul. You need to import confunc/cfconsul package

confunc provides a middleware mechanism via Interceptor type. It enables handling of various cases like default value

maxNumberOfOpenConnections := confunc.From(confunc.Env()).Int("MAX_OPEN_CONNECTIONS", confunc.Default("10"))
...
// when you need to access the value
if connectionCount < maxNumberOfOpenConnections() {
    // do your thing
}

Interceptor is a simple function that accepts a Confunc function and also returns Confunc function.

type Confunc func() (string, error)

type Interceptor func(Confunc) Confunc

Interceptors process the configuration value before it is accessed, every time. Custom interceptors can be easily introduces by providing a function matching the above signature. Available interceptors are:

• Default(defaultValue string) : returns a default value if there is no configuration made
• CacheOnce() : caches the value retrieved once and prevents accessing the configuration source each time
• CacheFor(cacheDuration time.Duration) : caches the value for a duration provided.