Refactor configuration management and enhance build process

- Introduced a YAML-based configuration system, allowing for automatic generation of a default `config.yaml` file.
- Updated the application to load configuration settings from the YAML file, improving flexibility and ease of use.
- Added a Makefile to streamline development tasks, including running the application, testing, and managing dependencies.
- Enhanced `.gitignore` to include build artifacts and configuration files.
- Removed unused Prometheus metrics and related code to simplify the codebase.
- Updated dependencies in `go.mod` and `go.sum` for improved functionality and performance.

config/config.go

@@ -0,0 +1,116 @@
+package config
+
+import (
+	"fmt"
+	"os"
+
+	"gopkg.in/yaml.v3"
+)
+
+type Config struct {
+	// Server configuration
+	ListenAddress string `yaml:"listen_address" default:":80"`
+
+	// Cache configuration
+	Cache CacheConfig `yaml:"cache"`
+
+	// Upstream configuration
+	Upstream string `yaml:"upstream"`
+}
+
+type CacheConfig struct {
+	// Memory cache settings
+	Memory MemoryConfig `yaml:"memory"`
+
+	// Disk cache settings
+	Disk DiskConfig `yaml:"disk"`
+}
+
+type MemoryConfig struct {
+	// Size of memory cache (e.g., "512MB", "1GB")
+	Size string `yaml:"size" default:"0"`
+
+	// Garbage collection algorithm: lru, lfu, fifo, largest, smallest, hybrid
+	GCAlgorithm string `yaml:"gc_algorithm" default:"lru"`
+}
+
+type DiskConfig struct {
+	// Size of disk cache (e.g., "10GB", "50GB")
+	Size string `yaml:"size" default:"0"`
+
+	// Path to disk cache directory
+	Path string `yaml:"path" default:""`
+
+	// Garbage collection algorithm: lru, lfu, fifo, largest, smallest, hybrid
+	GCAlgorithm string `yaml:"gc_algorithm" default:"lru"`
+}
+
+// LoadConfig loads configuration from a YAML file
+func LoadConfig(configPath string) (*Config, error) {
+	if configPath == "" {
+		configPath = "config.yaml"
+	}
+
+	data, err := os.ReadFile(configPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read config file %s: %w", configPath, err)
+	}
+
+	var config Config
+	if err := yaml.Unmarshal(data, &config); err != nil {
+		return nil, fmt.Errorf("failed to parse config file %s: %w", configPath, err)
+	}
+
+	// Set defaults for empty values
+	if config.ListenAddress == "" {
+		config.ListenAddress = ":80"
+	}
+	if config.Cache.Memory.Size == "" {
+		config.Cache.Memory.Size = "0"
+	}
+	if config.Cache.Memory.GCAlgorithm == "" {
+		config.Cache.Memory.GCAlgorithm = "lru"
+	}
+	if config.Cache.Disk.Size == "" {
+		config.Cache.Disk.Size = "0"
+	}
+	if config.Cache.Disk.GCAlgorithm == "" {
+		config.Cache.Disk.GCAlgorithm = "lru"
+	}
+
+	return &config, nil
+}
+
+// SaveDefaultConfig creates a default configuration file
+func SaveDefaultConfig(configPath string) error {
+	if configPath == "" {
+		configPath = "config.yaml"
+	}
+
+	defaultConfig := Config{
+		ListenAddress: ":80",
+		Cache: CacheConfig{
+			Memory: MemoryConfig{
+				Size:        "1GB",
+				GCAlgorithm: "lru",
+			},
+			Disk: DiskConfig{
+				Size:        "10GB",
+				Path:        "./disk",
+				GCAlgorithm: "hybrid",
+			},
+		},
+		Upstream: "",
+	}
+
+	data, err := yaml.Marshal(&defaultConfig)
+	if err != nil {
+		return fmt.Errorf("failed to marshal default config: %w", err)
+	}
+
+	if err := os.WriteFile(configPath, data, 0644); err != nil {
+		return fmt.Errorf("failed to write default config file: %w", err)
+	}
+
+	return nil
+}