I wouldn't invest that lump of money in one go. Generally, it is considered safer to spread out an investment of a lump-sum over a period time, even if just over a year. If the stock market dips 10% by July, you'll be regretting buying stocks only six months into the investment.
Second, the investment should be diversified. With 20k, perfect diversification isn't possible. I would at least break the investment into 4 chunks of 5k each and invest those separately.
1) Gold trade with limited time-horizon. The ETF with GLD is *the* way to trade gold because it is liquid. If the news changes which makes you think its time to sell gold in the business cycle, you can sell immediately with minimal commissions levied by your broker. The trade should be well executed, which requires knowledge of buy strategy and price movement that I will not explain here. I would set the upper limit of gold somewhere near $1,950 an ounce as a realistic target for the next year or so.
2) Invest in an oil company, or perhaps, an oil company ETF (so long as it does not have a huge stake in Exxon mobile or another large stake in one company, because then you might as well just buy that company's stock.) I do not know which oil company stock is best, as that requires doing weekly research.
3) Consider a company like Kellogg that has a 3% dividend yield. It's a staple goods company that has a mildly inverse relationship with oil. Let's say we woke up tomorrow to the possibility of a second recession/depression. At first, all stocks, including Kellogg's would decline. Once the crash or price correction was finished, Kellogg's stock would then soar. Also, if we hit a recession, oil prices would decline. Since Kellogg's profit increases when oil declines, their share price would soar even higher as their profitability improved. Expect such an investment to make you little to no money over your time frame, this investment seeks to be contrary to the other two commodity based investments. If those fail, this one succeeds and offsets your possible losses from the first two.
4) A growth stock, perhaps even a small cap that will have solid revenue growth in spite of a recession. These sorts of stocks are hard to find, but always worth owning as over the years, they'll rise no matter the economic conditions present, so long as the company's fundamentals are improving.
Don't own bonds, unless you plan on holding them to maturity, and are alright with low interest rates.