68 lines
1.5 KiB
Go
68 lines
1.5 KiB
Go
package config
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import (
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"os"
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"sync"
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)
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// OsFetcher is an implementation of the Fetcher type for communicating with
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// the system's environment.
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//
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// It is safe to use across multiple goroutines.
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type OsFetcher struct {
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// vmu guards read/write access to vals
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vmu sync.Mutex
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// vals maintains a local cache of the system's enviornment variables
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// for fast repeat lookups of a given key.
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vals map[string]*string
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}
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// NewOsFetcher returns a new *OsFetcher.
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func NewOsFetcher() *OsFetcher {
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return &OsFetcher{
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vals: make(map[string]*string),
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}
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}
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// Get returns the value associated with the given key as stored in the local
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// cache, or in the operating system's environment variables.
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//
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// If there was a cache-hit, the value will be returned from the cache, skipping
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// a check against os.Getenv. Otherwise, the value will be fetched from the
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// system, stored in the cache, and then returned. If no value was present in
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// the cache or in the system, an empty string will be returned.
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//
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// Get is safe to call across multiple goroutines.
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func (o *OsFetcher) Get(key string) (val string, ok bool) {
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o.vmu.Lock()
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defer o.vmu.Unlock()
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if i, ok := o.vals[key]; ok {
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if i == nil {
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return "", false
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}
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return *i, true
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}
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v, ok := os.LookupEnv(key)
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if ok {
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o.vals[key] = &v
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} else {
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o.vals[key] = nil
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}
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return v, ok
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}
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func (o *OsFetcher) All() map[string]string {
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return nil
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}
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func (o *OsFetcher) set(key, value string) {
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panic("cannot modify OS ENV keys")
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}
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func (o *OsFetcher) del(key string) {
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panic("cannot modify OS ENV keys")
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}
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