feat(cache):加入通用的缓存函数。

cache/abstract.go

@@ -0,0 +1,44 @@
+package cache
+
+import (
+	"electricity_bill_calc/global"
+	"time"
+
+	"github.com/go-redis/redis/v8"
+	"github.com/vmihailenco/msgpack/v5"
+)
+
+func Cache[T interface{}](key string, value *T, expires time.Duration) error {
+	serializedValue, err := msgpack.Marshal(value)
+
+	if err != nil {
+		return err
+	}
+	cmd := global.RedisConn.SetEX(global.Ctx, key, serializedValue, expires)
+	return cmd.Err()
+}
+
+func Retreive[T interface{}](key string) (*T, error) {
+	result, err := global.RedisConn.Get(global.Ctx, key).Result()
+	if err != nil {
+		if err == redis.Nil {
+			return nil, nil
+		} else {
+			return nil, err
+		}
+	}
+	value := new(T)
+	err = msgpack.Unmarshal([]byte(result), value)
+	if err != nil {
+		return nil, err
+	}
+	return value, nil
+}
+
+func Exists(key string) (bool, error) {
+	result, err := global.RedisConn.Exists(global.Ctx, key).Result()
+	if err != nil {
+		return false, err
+	}
+	return result > 0, nil
+}