opa: opa-wasm compile error

Describe the bug

A compile bug related with opa.OPA struct initialization.

A clear and concise description of what the bug is

I tried to use this SDK to realize a simple policy center but to find a very strange compile error:

/usr/local/Cellar/go/1.16.5/libexec/pkg/tool/darwin_amd64/link: 
running clang failed: exit status 1 Undefined symbols for architecture x86_64: 
 "_wasi_config_arg", referenced from:
      __cgo_cbbfd67d0eb3_Cfunc_wasi_config_arg in 000042.o
     (maybe you meant: __cgo_cbbfd67d0eb3_Cfunc_wasi_config_arg)
  "_wasi_config_capture_stderr", referenced from:
      __cgo_cbbfd67d0eb3_Cfunc_wasi_config_capture_stderr in 000042.o
     (maybe you meant: __cgo_cbbfd67d0eb3_Cfunc_wasi_config_capture_stderr)
  ... errors like the above...
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

After debug I found this error is related with the reference of opa.OPA in different packages. However, I failed to reproduce this error in a new project.

Steps to reproduce

The followings are probably the codes that trigger the error. I wrote the policycenter.go to realize a rules:

package policycenter

import (
	"context"
	"encoding/json"
	"fmt"
	"github.com/open-policy-agent/golang-opa-wasm/opa"
)

type PolicyCenter interface {
	Eval(entity *PolicyEntity, rego *opa.OPA) (*Result, error)
}

type Result struct {
	Result interface{}
}

type PolicyEntity struct {
	ctx        context.Context
	PolicyName string
	InputQuery interface{}
}

func NewPolicyEntity(ctx context.Context, policyName string, inputQuery interface{}) *PolicyEntity {
	return &PolicyEntity{
		ctx:        ctx,
		PolicyName: policyName,
		InputQuery: inputQuery,
	}
}

func Eval(entity *PolicyEntity, rego *opa.OPA) (*Result, error) {
	result, err := rego.Eval(entity.ctx, &entity.InputQuery)
	if err != nil {
		return nil, err
	}
	return &Result{result.Result}, nil
}

Then I wrote a main function in different packages and execute to check if it works:

package main

import (
	"goplayground/pkg/policycenter"
	"context"
	"fmt"
	"github.com/open-policy-agent/golang-opa-wasm/opa"
	"io/ioutil"
)

func main()  {
	input := map[string]interface{}{"Field1": "false", "Field2": "true"}
	wasmBytes, err := ioutil.ReadFile("policy.wasm")

	if err != nil {
		fmt.Printf("error: %v", err)
		return
	}

	rego, err := opa.New().WithPolicyBytes(wasmBytes).Init()

	if err != nil {
		fmt.Printf("error: %v\n", err)
		return
	}

	defer rego.Close()

	ctx := context.Background()
	entity := policycenter.NewPolicyEntity(
		ctx, "PA", input)
	result, _ := policycenter.Eval(entity, rego)
	res := result.Result.([]interface{})[0].(map[string]interface{})["result"].(string)
	fmt.Println(res)
}

Then the error occuered: I found out that I cannot declare *opa.OPA and policycenter.go at the same time in the main function I wrote above, if I only init opa.OPA or something in policycenter.go, the error won’t occur. Here is the example error occurring:

func main()  {
	wasmBytes, _ := ioutil.ReadFile("policy.wasm")
	rego, _ := opa.New().WithPolicyBytes(wasmBytes).Init()
	defer rego.Close()
}

func launchEval(rego *opa.OPA, entity *policycenter.PolicyEntity) {
	result, err := policycenter.Eval(entity, rego)
	if err != nil {
		fmt.Printf("error: %v\n", err)
		return
	}
	res := result.Result.([]interface{})[0].(map[string]interface{})["result"].(string)
	
	fmt.Println(res)
}

If I delete anything related with policycenter, the error will disappear.

Additional context

I wrote a policycenter_test.go in the same package of policycenter.go and it works well, it seems this compile error is related with opa.OPA reference and declaration in different packages. Here is the code:

package policycenter

import (
	"context"
	"fmt"
	"github.com/open-policy-agent/golang-opa-wasm/opa"
	"io/ioutil"
	"reflect"
	"sync"
	"testing"
)
var(
	cases = []interface{}{map[string]interface{}{"Fields1": "false", "Fields2": "true"},
		map[string]interface{}{"Fields1": "true", "Fields2": "true"},
		map[string]interface{}{"Fields1": "false", "Fields2": "false"},
	}
	ctx = context.Background()
	entity0 = NewPolicyEntity(ctx, "Policy", cases[0])
	entity1 = NewPolicyEntity(ctx, "Policy, cases[1])
	entity2 = NewPolicyEntity(ctx, "Policy", cases[2])
        input = []*PolicyEntity{entity0, entity1, entity2}
)



func TestEval(t *testing.T)  {
	var 
	wasmBytes, err := ioutil.ReadFile("../../policy.wasm")
	if err != nil {
		fmt.Printf("error: %v", err)
		return
	}

	rego, err := opa.New().WithPolicyBytes(wasmBytes).Init()

	if err != nil {
		fmt.Printf("error: %v\n", err)
		return
	}

	defer rego.Close()
	var wg sync.WaitGroup

	wg.Add(100)
	for i := 0; i < 100; i++ {
		go func() {
			t := i % 3
			launchEval(t, rego, input[t])
			wg.Done()
		}()
	}
	wg.Wait()

}

func launchEval(flag int, rego *opa.OPA, entity *PolicyEntity) {
	result, err := Eval(entity, rego)
	if err != nil {
		fmt.Printf("error: %v\n", err)
		return
	}
	res := result.Result.([]interface{})[0].(map[string]interface{})["result"].(string)
	switch flag {
	case 0:
		if res != "1P" {
			fmt.Println("failure occurs, expected 1P while get" + res)
		}
	case 1:
		if res != "2P" {
			fmt.Println("failure occurs, expected 2P while get" + res)
		}
	case 2:
		if res != "3P" {
			fmt.Println("failure occurs, expected 3P while get" + res)
		}
	}
}

and the test passed: this complie error confuses me a lot, why this error occurs?