package main

import (
   "os"
   "path/filepath"
)

func main() {
   file, err := os.Create("out.mp4")
   if err != nil {
      panic(err)
   }
   defer file.Close()
   data, err := os.ReadFile("_init_dec.mp4")
   if err != nil {
      panic(err)
   }
   file.Write(data)
   names, err := filepath.Glob("*.m4s")
   if err != nil {
      panic(err)
   }
   for _, name := range names {
      data, err := os.ReadFile(name)
      if err != nil {
         panic(err)
      }
      file.Write(data)
   }
}