what is a good dip for these shrimp?

Given the flavors in the shrimp (sriracha, cilantro, etc.) a Thai peanut sauce might be nice as a dip.

In addition to Pierino's great suggestions, you might also consider something cooling - like a yogurt-based dip, maybe with cucumber?

I think aioli would work (basically a garlic mayonaisse) but another suggestion would be to work some chopped really good anchovies (not the "pizza" ones) into good olive olive with perhaps some herb like oregano. Or you could go with a simple mayonaisse.