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Token server example, see http://goo.gl/QVCgcL
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| package main | |
| import ( | |
| "fmt" | |
| "time" | |
| ) | |
| type Token struct { | |
| token string | |
| expires time.Time | |
| } | |
| type TokenServer struct { | |
| getToken chan Token | |
| newToken chan Token | |
| token Token | |
| timer *time.Timer | |
| } | |
| func NewTokenServer() *TokenServer { | |
| s := &TokenServer{} | |
| s.getToken = make(chan Token) | |
| s.newToken = make(chan Token) | |
| go s.run() | |
| return s | |
| } | |
| func (s *TokenServer) run() { | |
| fmt.Println("TokenServer, starting...") | |
| // Initially, we have no token. Wait for one. | |
| go s.getNewToken() | |
| s.token = <-s.newToken | |
| fmt.Println("TokenServer, acquired token:", s.token.token) | |
| s.timer = time.NewTimer(s.token.expires.Sub(time.Now())) | |
| // We have a token, we can start serving clients. | |
| for { | |
| select { | |
| case s.getToken <- s.token: | |
| // Send token to client | |
| case s.token = <-s.newToken: | |
| // New token arrived. Schedule next refresh. | |
| fmt.Println("TokenServer, new token:", s.token.token) | |
| s.timer.Reset(s.token.expires.Sub(time.Now())) | |
| case <-s.timer.C: | |
| // Acquire new token (will send results on | |
| // s.newtoken) | |
| fmt.Println("TokenServer, getNewToken...") | |
| go s.getNewToken() | |
| } | |
| } | |
| } | |
| func (s *TokenServer) getNewToken() { | |
| // Simulate operation that takes long to complete | |
| time.Sleep(2 * time.Second) | |
| // Send result | |
| s.newToken <- Token{ | |
| token: "1234", | |
| expires: time.Now().Add(2 * time.Second), | |
| } | |
| } | |
| func (s *TokenServer) Get() Token { | |
| return <-s.getToken | |
| } | |
| func main() { | |
| s := NewTokenServer() | |
| fmt.Println(s.Get().token) | |
| time.Sleep(3 * time.Second) | |
| fmt.Println(s.Get().token) | |
| time.Sleep(8 * time.Second) | |
| fmt.Println(s.Get().token) | |
| } |
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