Enhance database configuration to support multiple data sources

- Updated .env.example to include optional configuration for additional database instances.
- Refactored DatabaseConfig in config.go to accommodate a default database and additional instances.
- Implemented loadAdditionalDBConfigs function to dynamically load configurations for extra databases.
- Modified InitDB function in database.go to establish connections for both default and additional databases.
- Updated README.md to document the new configuration options for connecting to multiple databases.

config/config.go

@@ -4,6 +4,7 @@ import (
 	"log"
 	"os"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/joho/godotenv"
@@ -27,6 +28,11 @@ type ServerConfig struct {
 }
 
 type DatabaseConfig struct {
+	Default    DatabaseInstanceConfig
+	Additional map[string]DatabaseInstanceConfig
+}
+
+type DatabaseInstanceConfig struct {
 	Host     string
 	Port     string
 	User     string
@@ -94,17 +100,22 @@ func LoadConfig() {
 		log.Println("未找到 .env 文件，使用环境变量")
 	}
 
+	defaultDB := DatabaseInstanceConfig{
+		Host:     getEnv("DB_HOST", "localhost"),
+		Port:     getEnv("DB_PORT", "3306"),
+		User:     getEnv("DB_USER", "root"),
+		Password: getEnv("DB_PASSWORD", ""),
+		DBName:   getEnv("DB_NAME", "wx_service"),
+	}
+
 	AppConfig = &Config{
 		Server: ServerConfig{
 			Port: getEnv("SERVER_PORT", "8080"),
 			Mode: getEnv("GIN_MODE", "debug"),
 		},
 		Database: DatabaseConfig{
-			Host:     getEnv("DB_HOST", "localhost"),
-			Port:     getEnv("DB_PORT", "3306"),
-			User:     getEnv("DB_USER", "root"),
-			Password: getEnv("DB_PASSWORD", ""),
-			DBName:   getEnv("DB_NAME", "wx_service"),
+			Default:    defaultDB,
+			Additional: loadAdditionalDBConfigs(defaultDB),
 		},
 		JWT: JWTConfig{
 			Secret: getEnv("JWT_SECRET", "your-secret-key"),
@@ -148,6 +159,30 @@ func LoadConfig() {
 	}
 }
 
+func loadAdditionalDBConfigs(defaultCfg DatabaseInstanceConfig) map[string]DatabaseInstanceConfig {
+	instances := strings.Split(getEnv("DB_INSTANCES", ""), ",")
+	result := make(map[string]DatabaseInstanceConfig)
+	for _, rawName := range instances {
+		name := strings.TrimSpace(rawName)
+		if name == "" {
+			continue
+		}
+		upperName := strings.ToUpper(name)
+		prefix := "DB_" + upperName + "_"
+		result[strings.ToLower(name)] = DatabaseInstanceConfig{
+			Host:     getEnv(prefix+"HOST", defaultCfg.Host),
+			Port:     getEnv(prefix+"PORT", defaultCfg.Port),
+			User:     getEnv(prefix+"USER", defaultCfg.User),
+			Password: getEnv(prefix+"PASSWORD", defaultCfg.Password),
+			DBName:   getEnv(prefix+"NAME", defaultCfg.DBName),
+		}
+	}
+	if len(result) == 0 {
+		return nil
+	}
+	return result
+}
+
 func getEnv(key, defaultValue string) string {
 	if value := os.Getenv(key); value != "" {
 		return value