function assigned to a package variable could not be detected with Call.

```go
package http_request

import (
	"context"
	"net/http"
)

var newRequestPkg = http.NewRequest

func _() {
	const url = "https://example.com"
	cli := &http.Client{}
	ctx := context.Background()
	req52, _ := newRequestPkg(http.MethodPost, url, nil) // TODO: false negative `net/http\.NewRequest must not be called. use net/http\.NewRequestWithContext`
	cli.Do(req52)
```