api: Add go files

I know this is a huge commit, but I can't be bothered to check
this in part by part.

api/utils_misc.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"bytes"
+	"os"
+)
+
+func concat(a bytes.Buffer, b bytes.Buffer) []byte {
+	return append(a.Bytes(), b.Bytes()...)
+}
+
+func exitIfError(err error) {
+	if err != nil {
+		os.Exit(1)
+	}
+}