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package config
import (
"os"
"sync"
)
// OsFetcher is an implementation of the Fetcher type for communicating with
// the system's environment.
//
// It is safe to use across multiple goroutines.
type OsFetcher struct {
// vmu guards read/write access to vals
vmu sync.Mutex
// vals maintains a local cache of the system's environment variables
// for fast repeat lookups of a given key.
vals map[string]*string
}
// NewOsFetcher returns a new *OsFetcher.
func NewOsFetcher() *OsFetcher {
return &OsFetcher{
vals: make(map[string]*string),
}
}
// Get returns the value associated with the given key as stored in the local
// cache, or in the operating system's environment variables.
//
// If there was a cache-hit, the value will be returned from the cache, skipping
// a check against os.Getenv. Otherwise, the value will be fetched from the
// system, stored in the cache, and then returned. If no value was present in
// the cache or in the system, an empty string will be returned.
//
// Get is safe to call across multiple goroutines.
func (o *OsFetcher) Get(key string) (val string, ok bool) {
o.vmu.Lock()
defer o.vmu.Unlock()
if i, ok := o.vals[key]; ok {
if i == nil {
return "", false
}
return *i, true
}
v, ok := os.LookupEnv(key)
if ok {
o.vals[key] = &v
} else {
o.vals[key] = nil
}
return v, ok
}
// GetAll implements the `config.Fetcher.GetAll` method by returning, at most, a
// 1-ary set containing the result of `config.OsFetcher.Get()`.
func (o *OsFetcher) GetAll(key string) []string {
if v, ok := o.Get(key); ok {
return []string{v}
}
return make([]string, 0)
}
func (o *OsFetcher) All() map[string][]string {
return nil
}
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