Add description about patch versions to README

README.md

@@ -185,6 +185,12 @@ steps:
 
 The `go-version-file` input accepts a path to a `go.mod` file or a `go.work` file that contains the version of Go to be used by a project.
 
+The `go` directive in `go.mod` can specify a patch version or omit it altogether (e.g., `go 1.22.0` or `go 1.22`).  
+If a patch version is specified, that specific patch version will be used.  
+If no patch version is specified, it will search for the latest available patch version in the cache,
+[versions-manifest.json](https://github.com/actions/go-versions/blob/main/versions-manifest.json), and the
+[official Go language website](https://golang.org/dl/?mode=json&include=all), in that order.
+
 If both the `go-version` and the `go-version-file` inputs are provided then the `go-version` input is used.
 > The action will search for the `go.mod` file relative to the repository root