HUhundt·Dec 8, 2013
Actually (https://github.com/gorilla/context/blob/master/context.go):
var (
mutex sync.Mutex
data = make(map[*http.Request]map[interface{}]interface{})
datat = make(map[*http.Request]int64)
)
// Set stores a value for a given key in a given request.
func Set(r *http.Request, key, val interface{}) {
mutex.Lock()
defer mutex.Unlock()
if data[r] == nil {
data[r] = make(map[interface{}]interface{})
datat[r] = time.Now().Unix()
}
data[r][key] = val
}
The map is needed because 'r' is not actually (and cannot be) modified, so for a later handler (for the same request) to access the data it must be stored in this map, so 'Get' can get it back. And the map is global, so you need a mutex.
As a side note, my understanding
Read the rest
is that it is not necessarily un-idiomatic to use a mutex in Go, particularly for shared state. See https://code.google.com/p/go-wiki/wiki/MutexOrChannel