Your employer has until January 31 to provide you with a W-2 either by mail or through a website. Make sure that your employers have your current mailing address. If you try to file a return without waiting for the W-2 and the IRS receives your W-2 then your tax return will either be rejected or the IRS will hold your tax return for several weeks or months to investigate the discrepancy.
If you do not receive the W-2 after early February, see this IRS website on how to proceed - https://www.irs.gov/uac/missing-form-w2-irs-can-help
See this TurboTax support FAQ for a missing W-2 - https://ttlc.intuit.com/questions/1901028-what-if-it-s-february-but-i-still-don-t-have-my-w-2
