Restore a struct that satisfy a defined interface from JSON string

I am implementing a task poller (restore unfinished task from a database).

The task must satisfy a defined Task interface:

type Task interface {
    // Identifier returns a unique string of a task
    Identifier() string
    // Data should be persistent
    Data() interface{}
    // Execute a task
    Execute()
}

The data stored in database satisfy the following struct:

type Record struct {
    Identifier string      `json:"identifier"`
    Data       interface{} `json:"data"`
}

When task poller starts, it read the stored data from the database, then (let's just ignore error handling for now):

r := &Record{}
result := database.Get(key)
json.Unmarshal([]byte(result), r)

we restored the saved data from the database into r.

A problem appears that I cannot call the Execute() method because r.Data is actually type of interface{} (map[string]interface{} more specifically ) other than type of Task.

How can I convert or transform the r.Data to become a struct that satisfies Task interface so that I can successfully call Execute() method?