Сниппет для POST отправки JSON string:
var jsonStr = []byte(`{"price":9899}`)
req, err := http.NewRequest(http.MethodPost, "https://example.com", bytes.NewBuffer(jsonStr))
if err != nil {
...
}
response, err := http.DefaultClient.Do(req)
if err != nil {
...
}
defer response.Body.Close()
_, err = ioutil.ReadAll(response.Body)
if err != nil {
...
}