People seem to be saying a) hold the cash and wait or b) put it in the market. There is a compromised path that exposes you to both scenarios (though by definition eliminates your ability to get the maximum possible upside).
Compromise: Put your cash in, for instance, Betterment's new 2.69% savings account so that it's at least earning reasonable interest for 2019. CIT online bank is another alternative at 2.4% for over $50k. Both are FDIC insured.
Take 10-30% of your cash holdings, divide by 12 and dollar-cost average your way into the (potentially bulging) market by making identical sized investments every month.
If we see a crash soon you've limited your downside exposure. If we keep growing you've exposed yourself to some upside. Recalibrate in a year or so.
I have 4 years of experience in client facing technical roles (and 3 years of experience in web and retail marketing).
patterncakes[at]gmail.com