取得交易對的當前市場價格

1{
2  "price": "100308.94" // current asset price
3}

1{
2  "state": 0,
3  "message": "Standard validation error"
4}

1{
2  "code": 0,
3  "message": "Validation failed.",
4  "errors": [
5    {
6      "property": "symbol",
7      "value": null,
8      "message": "This value should not be blank."
9    }
10  ]
11}