Config

Goal

A simple way to apply config settings to a Go app, when run locally, and in Docker/K8s, etc.

Strategy

• Use shell env vars to apply settings, this gives greatest flexibility and simplicity
• Return reasonable defaults, when a setting is un-configured.
• Simple and readable usage in code, at the point of use.

Usage

Update the defaultValues map with a setting you want to use, giving a reasonable default value.

In code we can retrieve a config setting like this:

import (
  "github.com/thisdougb/cleango/config"
)

func main() {

  var cfg *config.Config // dynamic config settings

  print(cfg.ValueAsStr("REDIS_HOST"))  // string at the point of use
  print(cfg.ValueAsInt("MAX_THREADS")) // int at the point of use
  print(cfg.ValueAsBool("DEBUG_ON"))   // bool at the point of use
}

An interesting side note is that settings are read dynamically, so we can change them in the environment without restarting the app.

Kubernetes Secrets

In the K8s manifest, create an env var from a secret like this:

env:
  - name: MYAPP_USERNAME
    valueFrom:
      secretKeyRef:
        name: myapp_credentials
        key: username
  - name: MYAPP_PASSWORD
    valueFrom:
      secretKeyRef:
        name: myapp_credentials
        key: password

And create the secret itself:

$ kubectl create secret generic myapp_credentials --from-literal=username=d3xg45sdf35 --from-literal=password=asdneqw234asck

Template Paths

Literal paths can be problematic between a dev env and production.

GetTemplatePath(fileName string) string

This method is included via Go build tags (dev or !dev), and gives a simple way to set a file path between environments. I use this to handle gohtml template files.

In your IDE/editor you need to ensure that your save/test actions are called with -tags dev.