Go app framework

pkg/config/config.go

@@ -0,0 +1,69 @@
+package config
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"os"
+	"runtime/debug"
+
+	"github.com/caarlos0/env/v9"
+	"gopkg.in/yaml.v3"
+)
+
+// To be set by ldflags in go build command or
+// retrieved from build meta below
+var Version = "(devel)"
+
+// Calling this will try to load from config if -config is
+// provided as a file, and will apply any environment overrides
+// on-top of configuration defaults.
+// Config is stored in returned context, and can be retrieved
+// using config.FromCtx(ctx)
+func LoadConfig(ctx context.Context) (context.Context, error) {
+	configPath := flag.String("config", "", "Path to the configuration file")
+	flag.Parse()
+
+	// Start with defaults
+	// Load from config if provided
+	// Layer on environment
+	cfg, err := loadConfig(*configPath)
+	if err != nil {
+		return ctx, err
+	}
+
+	// Add config to context, and return
+	// an updated context
+	ctx = cfg.AddToCtx(ctx)
+	return ctx, nil
+}
+
+func loadConfig(configPath string) (*AppConfig, error) {
+	cfg := newAppConfig()
+
+	if configPath != "" {
+		file, err := os.Open(configPath)
+		if err != nil {
+			return nil, fmt.Errorf("could not open config file: %w", err)
+		}
+		defer file.Close()
+
+		decoder := yaml.NewDecoder(file)
+		if err := decoder.Decode(cfg); err != nil {
+			return nil, fmt.Errorf("could not decode config file: %w", err)
+		}
+	}
+
+	if err := env.Parse(cfg); err != nil {
+		return nil, fmt.Errorf("could not parse environment variables: %w", err)
+	}
+
+	return cfg, nil
+}
+
+func getVersion() string {
+	if info, ok := debug.ReadBuildInfo(); ok && info.Main.Version != "(devel)" {
+		return info.Main.Version
+	}
+	return Version
+}