Lets play a community game!

4...c5!?

5. a5

a5 is not a valid move, @Dreki.

Cool!! We are waiting for rapid tactical complications! Black can look to the future with optimism.

5 b3

5...cxd4 good luck white

6. Qxd4 .... Luck is for the weak!

6...Qa5+!

7. Kd1

For more clearness:

1 d4 Nf6
2 Bg5 d5
3 e3 e6
4 c4 c5!?
5 b3 cxd4
6 Qxd4 Qa5+!
7 Ke1 ...