add note about 1.21.0 to README.md

README.md

@@ -2,6 +2,19 @@
 
 It's like actions/setup-go but faster.
 
+## A Note About Go 1.21.0
+
+**Use setup-go-faster@v1.9.0 or later** if you want to install Go 1.21.0.
+
+With the release of go1.21.0, the Go team has changed the way they publish
+dot-zero releases. They used to be styles go1.N, but now that are go1.N.0. This
+caused issues with earlier versions of setup-go-faster.
+
+**Do not user go-version: 1.21**. Use `go-version: 1.21.0`
+or `go-version: 1.21.x` instead.
+
+I should fix these inconsistencies soon.
+
 ### Faster
 
 Setup-go-faster takes about a third as long as setup-go to install go on a