mcp: finalize cleanup of Go 1.23, make Go version support explicit

Author: maciej-kisiel

.github/workflows/test.yml

@@ -40,7 +40,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: ["1.23", "1.24", "1.25"]
+        go: ["1.24", "1.25"]
     steps:
       - name: Check out code
         uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955 # v4

README.md

@@ -38,6 +38,9 @@ The following table shows which versions of the Go SDK support which versions of
 | v1.2.0+         | 2025-06-18        | 2025-11-25, 2025-06-18, 2025-03-26, 2024-11-05 |
 | v1.0.0 - v1.1.0 | 2025-06-18        | 2025-06-18, 2025-03-26, 2024-11-05             |
 
+New releases of the SDK target only supported versions of Go. See
+https://go.dev/doc/devel/release#policy for more information.
+
 ## Getting started
 
 To get started creating an MCP server, create an `mcp.Server` instance, add

internal/readme/README.src.md

@@ -37,6 +37,9 @@ The following table shows which versions of the Go SDK support which versions of
 | v1.2.0+         | 2025-06-18        | 2025-11-25, 2025-06-18, 2025-03-26, 2024-11-05 |
 | v1.0.0 - v1.1.0 | 2025-06-18        | 2025-06-18, 2025-03-26, 2024-11-05             |
 
+New releases of the SDK target only supported versions of Go. See
+https://go.dev/doc/devel/release#policy for more information.
+
 ## Getting started
 
 To get started creating an MCP server, create an `mcp.Server` instance, add

mcp/resource.go

@@ -113,6 +113,23 @@ func computeURIFilepath(rawURI, dirFilepath string, rootFilepaths []string) (str
 	return uriFilepathRel, nil
 }
 
+// withFile calls f on the file at join(dir, rel),
+// protecting against path traversal attacks.
+func withFile(dir, rel string, f func(*os.File) error) (err error) {
+	r, err := os.OpenRoot(dir)
+	if err != nil {
+		return err
+	}
+	defer r.Close()
+	file, err := r.Open(rel)
+	if err != nil {
+		return err
+	}
+	// Record error, in case f writes.
+	defer func() { err = errors.Join(err, file.Close()) }()
+	return f(file)
+}
+
 // fileRoots transforms the Roots obtained from the client into absolute paths on
 // the local filesystem.
 // TODO(jba): expose this functionality to user ResourceHandlers,