cannot read bytes from file with go after writing

So, i am trying to make a simple AOT virtual machine in golang, that reads a bytecode file as it's input. I am trying to very basically, write bytes to a file then read them with ioutil, however I am encountering a null dereference error.

This is my python code used for writing to the file:

btest = open("test.thief", "w")
bytes_to_write = bytearray([1, 44, 56, 55, 55, 0])

btest.write(bytes_to_write)

btest.close()

This is the code in my go file that I am using to read the bytes

package main

import (
   "fmt"
   "io/ioutil"
   "os"
)

func main() {
  //gets command line args
	userArgs := os.Args[1:]

    bytes, err := ioutil.ReadFile(userArgs[0]) // just pass the file name
    if err != nil {
        fmt.Print(err)
    }

     fmt.Println(bytes)
     machine := NewEnv()
     ReadBytes(machine, bytes)

}

And this is the error i am getting:

Joshuas-MacBook-Pro-3:thief Josh$ ./bin/Thief test.thief
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x2af3]

goroutine 1 [running]:
main.ReadBytes(0xc82000e390, 0xc82000c480, 0x6, 0x206)
    /Users/Josh/thief/src/Thief/read.go:26 +0x353
main.main()
    /Users/Josh/thief/src/Thief/Main.go:18 +0x1f2

I have also tried opening the file in binary mode with the python code, but it produces the same error. Basically the goal of this is that I want to be able to extract an array of bytes but also have a way to write theme.

Am i writing the bytes incorrectly?

Here is the hexdump:

012c 3837 3700

EDIT:

This is the rest of my go files

opfuncs.go

package main


//file for machine functions and operations

//prints string format of some bytes
func print(env Env, data []byte) {
	fmt.Println(string(data))
}


var OPERS map[byte]func(Env, []byte)

//0 is reserved as the null terminator
func init(){
	OPERS = map[byte]func(Env, []byte){
		1:print,
	}
}

env.go

package main


//file for the env struct



type Env struct {
	items map[string]interface{}
}

func NewEnv() Env {
	return Env{make(map[string]interface{})}
}

//general getter
func (self *Env) get(key string) interface{} {
	val, has := self.items[key]
	if has {
		return val
	} else {
		return nil
	}
}

//general setter
func (self *Env) set(key string, value interface{}) {
	self.items[key] = value
}

func (self *Env) contains(key string) bool {
	_, has := self.items[key]
	return has
}

func (self *Env) declare(key string) {
	self.items[key] = Null{}
}

func (self *Env) is_null(key string) bool {
	_, ok := self.items[key].(Null)
	return ok
}

//deletes an item from storage
func (self *Env) del(key string) {
	delete(self.items, key)
}

read.go

package main

//file that contains the reading function for the VM

func ReadBytes(env Env, in []byte) {
	bytes := make([]byte, 1)
	fn := byte(0)
	mode := 0
	for i:=0;i<len(in);i++ {
		switch mode {
		case 0:
			fn = byte(i)
			mode = 1
		case 1:
			if i != len(in)-1 {
				if in[i+1] == 0 {
					bytes = append(bytes, in[i])
					mode = 2
				} else {
					bytes = append(bytes, in[i])
				}
			} else {
				bytes = append(bytes, in[i])
			}
		case 2:
			OPERS[fn](env, bytes)
			mode = 0
			fn = byte(0)
			bytes = make([]byte, 1)
		}
	}
}

If you use Python 3, the file must be opened in the binary mode:

btest = open("test.thief", "wb")

It looks like you're not writing to the file in your python code?

I get

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: write() argument must be str, not bytearray

After your third line which would explain why golang can't find the file contents.

Also you're not using bytes so your gocode won't compile. Do this instead.

package main

import (
   "fmt"
   "io/ioutil"
   "os"
)

func main() {
  //gets command line args
    userArgs := os.Args[1:]

    _, err := ioutil.ReadFile(userArgs[0]) // just pass the file name
    if err != nil {
        fmt.Print(err)
    }

}