diff --git a/.github/workflows/go-generate.yml b/.github/workflows/go-generate.yml
new file mode 100644
index 0000000..349bf01
--- /dev/null
+++ b/.github/workflows/go-generate.yml
@@ -0,0 +1,23 @@
+on: [push, pull_request]
+name: go generate
+
+jobs:
+  gogenerate:
+    strategy:
+      fail-fast: false
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: recursive
+      - uses: actions/setup-go@v2
+        with:
+          go-version: "1.16.x"
+      - name: Go information
+        run: |
+          go version
+          go env
+      - name: Run go generate
+        run: |
+          go generate ./...
+          git diff --exit-code
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..d94c248
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "multicodec"]
+	path = multicodec
+	url = https://github.com/multiformats/multicodec
diff --git a/gen.go b/gen.go
index 4b0cc78..25cfd6d 100644
--- a/gen.go
+++ b/gen.go
@@ -7,7 +7,6 @@ import (
 	"encoding/csv"
 	"io"
 	"log"
-	"net/http"
 	"os"
 	"strings"
 	"text/template"
@@ -69,14 +68,14 @@ func (c tableEntry) VarName() string {
 }
 
 func main() {
-	resp, err := http.Get("https://raw.githubusercontent.com/multiformats/multicodec/HEAD/table.csv")
+	f, err := os.Open("multicodec/table.csv")
 	if err != nil {
 		log.Fatal(err)
 	}
-	defer resp.Body.Close()
+	defer f.Close()
 
 	var entries []tableEntry
-	csvReader := csv.NewReader(resp.Body)
+	csvReader := csv.NewReader(f)
 	csvReader.Read() // skip the header line
 	for {
 		record, err := csvReader.Read()
diff --git a/multicodec b/multicodec
new file mode 160000
index 0000000..b1bf92f
--- /dev/null
+++ b/multicodec
@@ -0,0 +1 @@
+Subproject commit b1bf92f815c8a9b2a57c667ac5a1104683cc48a6