[react]react 执行npm run build后，fetch访问本地json报错

getJSON(){
        var that =this;
        fetch('./product.json')
            .then(function(response) {
                return response.json()
            }).then(function(json) {
                console.log(json)
                console.log(this)
                that.setState({
                   product:json
               })
            }).catch(function(ex) {
                console.log('parsing failed', ex)
            })
    }

图片：product.jpg