opa.go

func (this *usersService) IsMagicLinkVerified(ctx context.Context, in *users.IsMagicLinkVerifiedRequest) (*users.IsMagicLinkVerifiedResponse, error) {
	c, _ := context.WithDeadline(ctx, time.Now().Add(25*time.Second))
	ticker := ImmediateTicker(c, time.Second)
	for {
		select {
		case <-c.Done():
			return &users.IsMagicLinkVerifiedResponse{Status: users.MagicLinkStatus_unknown}, nil
		case <-ticker:
			status, token := this.tokensRepo.IsMagicLinkVerified(in.SessionId)
			if status != users.MagicLinkStatus_unknown {
				return &users.IsMagicLinkVerifiedResponse{
					Status: status,
					Token:  token,
				}, nil
			}
		}
	}
}

a couple of interesting points

• line 2 -> merging the HTTP context with a timeout
• line 6 -> awaits to whichever ever event happens first, the timeout or the connection is closed ( say if load balancer closes it )
• line 8 -> ticking every second and asking tokensRepo ( redis ) if a key exists
• line 10 -> if status is unknown ( we still wait ) -> continue infinite loop
• line 11 -> if the key exists in redis, return response

Notice, no Promises or Futures or any multi-threading communication.
this is 100% async, every time the goroutine is awaiting ( say between the ticks ) No thread is blocked.

I think this is super cool !