Server instances with multiple users

Question

I\'m new to Go and I have the following problem. I tried to simplify it: I have a server which has for example a global variable myvar. All users can POST the endpo

Answer 1

Requests are served from multiple goroutines, concurrently. This means if they read/write the same variable, access to this variable must be synchronized.

Next, if you want a different instance of this data for each user, you may use a map, mapping from user ID or name to the data structure.

Let's assume the data structure is a struct, e.g.:

type customData struct {
    Field1 string
    Field2 int
    // Whatever fields you need
}

The map holding one for each user:

var userDataMap = map[string]customData{}

You may use a sync.RWMutex for protecting a map while it is read / written from a goroutine:

var mu = &sync.RWMutex{}

And synchronized access to the map, using the above mutex:

func Get(user string) customData {
    mu.RLock()
    defer mu.RUnlock()
    return userDataMap[user]
}

func Set(user string, data customData) {
    mu.Lock()
    userDataMap[user] = data
    mu.Unlock()
}

Another, more sophisticated solution would be to use server side HTTP sessions. For details, see Go session variables?