The Google URL Shortener (goo.gl) was launched in December 2009, originally intended to be used with Google Toolbar and Feedburner. However, the need for link shorteners has largely gone away over the past few years, and goo.gl started to wind down last year. It was already unavailable to new users as of May 2018, but now it's gone for everyone.
Existing goo.gl links will still work, but it's now impossible to create new ones. The company recommends that app developers switch to Firebase Dynamic Links, and users to switch to Bit.ly and Ow.ly. Rest in peace goo.gl, you had a good run.