我正在嘗試使用Go作為教程構(gòu)建一個(gè)基本的緩存系統(tǒng)。由于某種原因，當(dāng)我運(yùn)行這個(gè)時(shí)，if else語句會(huì)導(dǎo)致錯(cuò)誤。package datasourceimport (    "fmt"    "github.com/patrickmn/go-cache"    "time")type DataSource interface {    Value(key string) (interface{}, error)}// DataSourceStr type, implements the DataSource interfacetype DataSourceStr struct {    data map[string]string}var cache = cache.New(5*time.Minute, 5*time.Minute)func (n *DataSourceStr) Value(key string) (interface{}, error) {        /*     1. Compute a cache key    2. Search cache key    3. If hit return value    4. If miss, do datasource    5. Cache and return slow thing.    */        cached, found := cache.Value(key)    if found {        return cached, nil    }    else if _, ok := n.data[key]; ok     {        //measure how often a key gets called.        cache.Set(key, n.data[key], cache.DefaultExpiration)        return n.data[key], nil    } else {        return nil, fmt.Errorf("key not found %v", ok)    }}func getFromDS(datasource DataSource, key string) (string, error) {        v, err := datasource.Value(key)        //create a map that decays based on time.    if err != nil {        return "", nil    }    return fmt.Sprint(v), nil}我做錯(cuò)了什么？我正在嘗試輸入一個(gè)密鑰，然后從緩存或數(shù)據(jù)庫中返回值。不知道我在語法上做錯(cuò)了什么！