Go HTTP Server with OTEL Template

pkg/config/config.go

@@ -0,0 +1,69 @@
+package config
+
+import (
+	"flag"
+	"fmt"
+	"os"
+
+	"github.com/caarlos0/env/v9"
+	"gopkg.in/yaml.v3"
+)
+
+type AppConfig struct {
+	Name        string     `yaml:"name" env:"APP_NAME" envDefault:"go-http-server-with-otel"`
+	Environment string     `yaml:"environment" env:"APP_ENVIRONMENT" envDefault:"development"`
+	Version     string     `yaml:"version" env:"APP_VERSION"`
+	Logging     LogConfig  `yaml:"logging"`
+	HTTP        HTTPConfig `yaml:"http"`
+	OTEL        OTELConfig `yaml:"otel"`
+}
+
+type LogConfig struct {
+	Enabled bool   `yaml:"enabled" env:"APP_LOGGING_ENABLED" envDefault:"true"`
+	Level   string `yaml:"level" env:"APP_LOGGING_LEVEL" envDefault:"info"`
+	Format  string `yaml:"format" env:"APP_LOGGING_FORMAT" envDefault:"json"`
+}
+
+type HTTPConfig struct {
+	Listen         string `yaml:"listen" env:"APP_HTTP_LISTEN" envDefault:"127.0.0.1:8080"`
+	RequestTimeout int    `yaml:"request_timeout" env:"APP_HTTP_REQUEST_TIMEOUT" envDefault:"30"`
+}
+
+type OTELConfig struct {
+	Enabled           bool   `yaml:"enabled" env:"APP_OTEL_ENABLED" envDefault:"true"`
+	PrometheusEnabled bool   `yaml:"prometheus_enabled" env:"APP_OTEL_PROMETHEUS_ENABLED" envDefault:"true"`
+	PrometheusPath    string `yaml:"prometheus_path" env:"APP_OTEL_PROMETHEUS_PATH" envDefault:"/metrics"`
+}
+
+// Calling this will try to load from config if -config is
+// provided, otherwise will return *AppConfig with defaults,
+// performing any environment substitutions
+func LoadConfig() (*AppConfig, error) {
+	configPath := flag.String("config", "", "Path to the configuration file")
+	flag.Parse()
+
+	return loadConfig(*configPath)
+}
+
+func loadConfig(configPath string) (*AppConfig, error) {
+	cfg := AppConfig{}
+
+	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
+}

pkg/config/ctx.go

@@ -0,0 +1,28 @@
+package config
+
+import (
+	"context"
+	"errors"
+)
+
+type appConfigKey uint8
+
+const appConfigCtxKey appConfigKey = iota
+
+func (a *AppConfig) AddToCtx(ctx context.Context) context.Context {
+	return context.WithValue(ctx, appConfigCtxKey, a)
+}
+
+func FromCtx(ctx context.Context) (*AppConfig, error) {
+	ctxData := ctx.Value(appConfigCtxKey)
+	if ctxData == nil {
+		return nil, errors.New("no config found in context")
+	}
+
+	cfg, ok := ctxData.(*AppConfig)
+	if !ok {
+		return nil, errors.New("invalid config stored in context")
+	}
+
+	return cfg, nil
+}