Reading configuration across packages

One of the nicer features of having Viper manage your configuration in its own singleton is that you can read your configuration across packages, so long as you've already executed your viper initialization when you work with your other packages.

So as an example, I'll create a new directory (to represent a new package, or module) called backends, and I'll write a small function that enumerates my backends.

I'm running this from my project's base directory.

mkdir backends
echo package backends >> backends/backends.go

I have this sample function Enumerate. The logic isn't super important.

package backends

import (
	"fmt"

	"github.com/spf13/viper"
)

func Enumerate() {
	fmt.Println("Hello from the backends package!")
	backends := viper.GetStringSlice("backends")
	for i, backend := range backends {
		fmt.Printf("%d: %s\n", i, backend)
	}
}

What is important is that you notice that I've simply called viper.GetStringSlice directly. Access to configuration entries is vastly simplified using tools like Viper. This is also made possible because we've leveraged our main.go's init function to configure Viper, and that doing so causes that configuration to take place well before any of this code is called.

Add this to your main function and see that it works as expected.

func main() {
    // ... unchanged ...

	backends.Enumerate()
}

And the result is as expected!

$ go run .
# ... unchanged ...
Hello from the backends package!
0: 192.168.10.01:8001
1: 192.168.10.01:8002
2: 192.168.10.01:8003
3: 192.168.10.01:8004