fix: properly convert int to string

I'm new to Go, sorry.
Btw, IT WORKS NOW!!

server.go

@@ -6,6 +6,7 @@ import (
 	"database/sql"
 	"fmt"
 	"os"
+	"strconv"
 	"strings"
 
 	_ "github.com/mattn/go-sqlite3"
@@ -84,7 +85,7 @@ func handler(ctx *fasthttp.RequestCtx) {
 	ctx.Response.SetStatusCode(code)
 
 	// -- find in FS and read headers+body
-	path := "storage/" + string(id)
+	path := "storage/" + strconv.Itoa(id)
 
 	fh, err := os.Open(path + "/headers")
 	if err != nil {