install go2rtc on bob

installs_on_host/go2rtc/pkg/hap/hkdf/hkdf.go

@@ -0,0 +1,17 @@
+package hkdf
+
+import (
+	"crypto/sha512"
+	"io"
+
+	"golang.org/x/crypto/hkdf"
+)
+
+func Sha512(key []byte, salt, info string) ([]byte, error) {
+	r := hkdf.New(sha512.New, key, []byte(salt), []byte(info))
+
+	buf := make([]byte, 32)
+	_, err := io.ReadFull(r, buf)
+
+	return buf, err
+}