Shared critical section for true synchronization

shared_critical_section_for_coroutines.kt

suspend fun obtainAccessToken(): String {
    val kCriticalSection = DI.get<KCriticalSection>(qualifier = "shared")
    
    return kCriticalSection.synchronized {
        val accessToken = readAccessTokenFromStorageOrMemory() // might be a suspending call

        if (accessToken != null && System.currentTimeMillis() < accessToken.createdAt + accessToken.expiresIn) {
            return@synchronized accessToken.toString() // access token is valid
        }

        val refreshToken = readRefreshTokenFromSecureStorage() // normally a suspending call

        // normally suspending as it makes another API call
        val newAccessToken = performTokenRefresh(
            accessToken = accessToken,
            refreshToken = refreshToken
        )

        saveAccessTokenToStorageOrMemory(newAccessToken) // might be a suspending call
        return@synchronized newAccessToken.toString()
    }
}