docs: move auto-detect go.mod docs to advanced-usage.md

Follows the pattern from #724 where detailed usage docs live in
docs/advanced-usage.md rather than README.md.

README.md

@@ -102,18 +102,6 @@ For details on Semantic Versioning, see [the semver package documentation](https
 >
 > The recommendation is based on the YAML parser's behavior, which interprets non-wrapped values as numbers and, in the case of version `1.20`, trims it down to `1.2`, which may not be very obvious.
 
-### Automatic go.mod detection
-
-**New in v6**: If neither `go-version` nor `go-version-file` is specified, the action will automatically look for a `go.mod` file in the repository root and use the Go version specified in it. This simplifies workflows for projects that already have a `go.mod` file.
-
-```yaml
-steps:
-  - uses: actions/checkout@v6
-  - uses: actions/setup-go@v6
-    # Automatically uses go.mod from repository root
-  - run: go version
-```
-
 For more usage examples, please refer to the section: [Using go-version input](docs/advanced-usage.md#using-the-go-version-input) of the [Advanced usage](docs/advanced-usage.md) guide.
 
 ## Recommended permissions

docs/advanced-usage.md

@@ -168,6 +168,18 @@ jobs:
 
 If both the `go-version` and the `go-version-file` inputs are provided then the `go-version` input is used. The `.tool-versions` file supports version specifications in accordance with asdf standards, adhering to Semantic Versioning ([semver](https://semver.org)).
 
+### Automatic go.mod detection
+
+If neither `go-version` nor `go-version-file` is specified, the action will automatically look for a `go.mod` file in the repository root and use the Go version specified in it. This simplifies workflows for projects that already have a `go.mod` file.
+
+```yaml
+steps:
+  - uses: actions/checkout@v6
+  - uses: actions/setup-go@v6
+    # Automatically uses go.mod from repository root
+  - run: go version
+```
+
 ```yaml
 steps:
   - uses: actions/checkout@v6