Add get task/id (#30)

Closes #22

Reviewed-on: #30

backend/db.go

@@ -200,3 +200,14 @@ func (db *Db) GetTasks() ([]Task, error) {
 	}
 	return tasks, nil
 }
+
+func (db *Db) GetTask(id int) (Task, error) {
+	task := Task{}
+
+	err := db.db.Query("select id, name, reward, assigned from tasks where id = ?").
+		Bind(id).ScanSingle(&task.ID, &task.Name, &task.Reward, &task.Assigned)
+	if err != nil {
+		return Task{}, err
+	}
+	return task, nil
+}