update README.md; gen-keypair utility

utils/gen-keypair.go

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"crypto/ed25519"
+	"crypto/rand"
+	"encoding/base64"
+	"fmt"
+	"os"
+)
+
+func main() {
+	// rand.Reader uses /dev/urandom on Linux
+	pub, priv, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error: %s\n", err.Error())
+		os.Exit(1)
+	}
+
+	fmt.Fprintf(os.Stdout, "JWT_PUBLIC_KEY=%#v\nJWT_PRIVATE_KEY=%#v\n",
+		base64.StdEncoding.EncodeToString(pub),
+		base64.StdEncoding.EncodeToString(priv))
+}