Use go-fsimpl to read from datasources

Signed-off-by: Dave Henderson <[email protected]>

context.go

@@ -22,9 +22,16 @@ func (c *tmplctx) Env() map[string]string {
 }
 
 // createTmplContext reads the datasources for the given aliases
-//
-//nolint:staticcheck
-func createTmplContext(_ context.Context, aliases []string, d *data.Data) (interface{}, error) {
+func createTmplContext(ctx context.Context, aliases []string,
+	//nolint:staticcheck
+	d *data.Data) (interface{}, error) {
+	// we need to inject the current context into the Data value, because
+	// the Datasource method may need it
+	// TODO: remove this before v4
+	if d != nil {
+		d.Ctx = ctx
+	}
+
 	var err error
 	tctx := &tmplctx{}
 	for _, a := range aliases {

context_test.go

@@ -6,7 +6,9 @@ import (
 	"os"
 	"testing"
 
+	"github.com/hairyhenderson/go-fsimpl"
 	"github.com/hairyhenderson/gomplate/v4/data"
+	"github.com/hairyhenderson/gomplate/v4/internal/datafs"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -31,6 +33,11 @@ func TestCreateContext(t *testing.T) {
 	require.NoError(t, err)
 	assert.Empty(t, c)
 
+	fsmux := fsimpl.NewMux()
+	fsmux.Add(datafs.EnvFS)
+
+	ctx = datafs.ContextWithFSProvider(ctx, fsmux)
+
 	fooURL := "env:///foo?type=application/yaml"
 	barURL := "env:///bar?type=application/yaml"
 	uf, _ := url.Parse(fooURL)