Add internal/config package

internal/config/config.go

@@ -0,0 +1,40 @@
+package config
+
+import (
+	"os"
+	"time"
+)
+
+// Config holds runtime configuration for the server, sourced from the
+// environment.
+type Config struct {
+	Addr         string
+	ReadTimeout  time.Duration
+	WriteTimeout time.Duration
+}
+
+// Load reads configuration from environment variables, falling back to
+// sensible defaults when a variable is unset.
+func Load() Config {
+	return Config{
+		Addr:         getString("ADDR", ":8080"),
+		ReadTimeout:  getDuration("READ_TIMEOUT", 5*time.Second),
+		WriteTimeout: getDuration("WRITE_TIMEOUT", 10*time.Second),
+	}
+}
+
+func getString(key, fallback string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return fallback
+}
+
+func getDuration(key string, fallback time.Duration) time.Duration {
+	if v := os.Getenv(key); v != "" {
+		if d, err := time.ParseDuration(v); err == nil {
+			return d
+		}
+	}
+	return fallback
+}

internal/config/config_test.go

@@ -0,0 +1,49 @@
+package config
+
+import (
+	"testing"
+	"time"
+)
+
+func TestLoadDefaults(t *testing.T) {
+	t.Setenv("ADDR", "")
+	t.Setenv("READ_TIMEOUT", "")
+	t.Setenv("WRITE_TIMEOUT", "")
+
+	cfg := Load()
+	if cfg.Addr != ":8080" {
+		t.Errorf("Addr = %q, want :8080", cfg.Addr)
+	}
+	if cfg.ReadTimeout != 5*time.Second {
+		t.Errorf("ReadTimeout = %v, want 5s", cfg.ReadTimeout)
+	}
+	if cfg.WriteTimeout != 10*time.Second {
+		t.Errorf("WriteTimeout = %v, want 10s", cfg.WriteTimeout)
+	}
+}
+
+func TestLoadOverrides(t *testing.T) {
+	t.Setenv("ADDR", ":9090")
+	t.Setenv("READ_TIMEOUT", "2s")
+	t.Setenv("WRITE_TIMEOUT", "20s")
+
+	cfg := Load()
+	if cfg.Addr != ":9090" {
+		t.Errorf("Addr = %q, want :9090", cfg.Addr)
+	}
+	if cfg.ReadTimeout != 2*time.Second {
+		t.Errorf("ReadTimeout = %v, want 2s", cfg.ReadTimeout)
+	}
+	if cfg.WriteTimeout != 20*time.Second {
+		t.Errorf("WriteTimeout = %v, want 20s", cfg.WriteTimeout)
+	}
+}
+
+func TestLoadInvalidDurationFallsBack(t *testing.T) {
+	t.Setenv("READ_TIMEOUT", "not-a-duration")
+
+	cfg := Load()
+	if cfg.ReadTimeout != 5*time.Second {
+		t.Errorf("ReadTimeout = %v, want fallback 5s", cfg.ReadTimeout)
+	}
+}