feat(story-1.2): add database migration system with golang-migrate

internal/config/config.go

@@ -0,0 +1,41 @@
+// Package config handles application configuration from environment variables.
+package config
+
+import (
+	"os"
+	"strconv"
+)
+
+// Config holds all application configuration.
+type Config struct {
+	Port        string
+	DatabaseURL string
+	Environment string
+}
+
+// Load reads configuration from environment variables with sensible defaults.
+func Load() *Config {
+	return &Config{
+		Port:        getEnv("PORT", "8080"),
+		DatabaseURL: getEnv("DATABASE_URL", "postgres://flowreader:flowreader@db:5432/flowreader?sslmode=disable"),
+		Environment: getEnv("ENV", "development"),
+	}
+}
+
+// getEnv returns the value of an environment variable or a default value.
+func getEnv(key, defaultValue string) string {
+	if value, exists := os.LookupEnv(key); exists {
+		return value
+	}
+	return defaultValue
+}
+
+// getEnvInt returns an integer environment variable or a default value.
+func getEnvInt(key string, defaultValue int) int {
+	if value, exists := os.LookupEnv(key); exists {
+		if intValue, err := strconv.Atoi(value); err == nil {
+			return intValue
+		}
+	}
+	return defaultValue
+}