renderFile.go

func renderFile(d *schema.ResourceData) (string, error) {

	var err error

	tf := template.FuncMap{
		"isInt": func(i interface{}) bool {
			v := reflect.ValueOf(i)
			switch v.Kind() {
			case reflect.Int, reflect.Int8, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint32, reflect.Uint64, reflect.Float32, reflect.Float64:
				return true
			default:
				return false
			}
		},
		"isString": func(i interface{}) bool {
			v := reflect.ValueOf(i)
			switch v.Kind() {
			case reflect.String:
				return true
			default:
				return false
			}
		},
		"isSlice": func(i interface{}) bool {
			v := reflect.ValueOf(i)
			switch v.Kind() {
			case reflect.Slice:
				return true
			default:
				return false
			}
		},
		"isArray": func(i interface{}) bool {
			v := reflect.ValueOf(i)
			switch v.Kind() {
			case reflect.Array:
				return true
			default:
				return false
			}
		},
		"isMap": func(i interface{}) bool {
			v := reflect.ValueOf(i)
			switch v.Kind() {
			case reflect.Map:
				return true
			default:
				return false
			}
		},
	}

	var data string // data from tf
	data = d.Get("data").(string)

	// unmarshal json from data into m
	var m = make(map[string]interface{}) // unmarshal data into m
	if err = json.Unmarshal([]byte(data), &m); err != nil {
		panic(err)
	}

	templateFile := d.Get("template").(string)
	t, err := template.ParseFiles(templateFile)
	if err != nil {
		panic(err)
	}

	var contents bytes.Buffer // io.writer for template.Execute
	tt := t.Funcs(tf)
	if tt != nil {
		err = tt.Execute(&contents, m)
		if err != nil {
			return "", templateRenderError(fmt.Errorf("failed to render %v", err))
		}
	} else {
		return "", templateRenderError(fmt.Errorf("error: %v", err))
	}

	return contents.String(), nil
}