main.go

package main

import (
	"fmt"

	"../runtime"
)

func main() {
	r, err := runtime.NewRuntime("simple.wasm")
	if err != nil { panic(err) }
  
	result, err := r.Main()
	if err != nil { panic(err) }
  
	log.Println("got:", result)
  }

wasm.go

package runtime

import (
	wasm "github.com/wasmerio/go-ext-wasm/wasmer"
)

type Runtime struct {
	vm wasm.Instance
}

func NewRuntime(fp string) (*Runtime, error) {
	// Reads the WebAssembly module as bytes.
	bytes, err := wasm.ReadBytes(fp)
	if err != nil {
		return nil, err
	}

	// Instantiates the WebAssembly module.
	instance, err := wasm.NewInstance(bytes)
	if err != nil {
		return nil, err
	}

	return &Runtime{
		vm:   instance,
	}, nil
}
func (r Runtime) Main() (wasm.Value, error) {
    main, ok := r.vm.Exports["main"]
    if !ok {
      return wasm.Value{}, fmt.Errorf("can't find main function")
    } 
	return main()
}

wasm_test.go

package runtime

import (
	"io"
	"net/http"
	"os"
	"path/filepath"
	"testing"
)

const RUNTIME_WASM string = "../simple.wasm"
const RUNTIME_WASM_URL string = "https://github.com/xyz/target/wasm32-unknown-unknown/debug/simple.wasm?raw=true"

// getRuntimeBlob checks if the runtime wasm file exists and if not get it from github

func getRuntimeBlob() (n int64, err error) {
	if Exists(RUNTIME_WASM) {
		return 0, nil
	}

	out, err := os.Create(RUNTIME_WASM)
	if err != nil {
		return 0, err
	}
	defer out.Close()

	resp, err := http.Get(RUNTIME_WASM_URL)
	if err != nil {
		return 0, err
	}
	defer resp.Body.Close()

	n, err = io.Copy(out, resp.Body)
	return n, err
}

// Exists reports whether the named file or directory exists.
func Exists(name string) bool {
	if _, err := os.Stat(name); err != nil {
		if os.IsNotExist(err) {
			return false
		}
	}
	return true
}

func newRuntime(t *testing.T) (*Runtime, error) {
    _, err := getRuntimeBlob()
    if err != nil {
        t.Fatalf("Fail: could not get wasm file")
    }

    fp, err := filepath.Abs(RUNTIME_WASM)
    if err != nil {
        t.Fatal("could not create filepath")
    }

    r, err := NewRuntime(fp)
    if err != nil {
        t.Fatal(err)
    } else if r == nil {
        t.Fatal("did not create new VM")
    }

    return r, err
}