curl --request POST \
  --url https://whitebit.com/api/v4/main-account/smart-flex/investments \
  --header 'Content-Type: application/json' \
  --header 'X-TXC-APIKEY: <api-key>' \
  --header 'X-TXC-PAYLOAD: <api-key>' \
  --header 'X-TXC-SIGNATURE: <api-key>' \
  --data '
{
  "limit": 100,
  "offset": 0,
  "ticker": "USDT",
  "plan": "8f2e9d3c-1a4b-4c2d-9e5f-6a7b8c9d0e1f",
  "investment": "invest_id_123",
  "investmentStatus": 1,
  "request": "{{request}}",
  "nonce": 1594297865000
}
'

import requests

url = "https://whitebit.com/api/v4/main-account/smart-flex/investments"

payload = {
    "limit": 100,
    "offset": 0,
    "ticker": "USDT",
    "plan": "8f2e9d3c-1a4b-4c2d-9e5f-6a7b8c9d0e1f",
    "investment": "invest_id_123",
    "investmentStatus": 1,
    "request": "{{request}}",
    "nonce": 1594297865000
}
headers = {
    "X-TXC-APIKEY": "<api-key>",
    "X-TXC-PAYLOAD": "<api-key>",
    "X-TXC-SIGNATURE": "<api-key>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {
    'X-TXC-APIKEY': '<api-key>',
    'X-TXC-PAYLOAD': '<api-key>',
    'X-TXC-SIGNATURE': '<api-key>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    limit: 100,
    offset: 0,
    ticker: 'USDT',
    plan: '8f2e9d3c-1a4b-4c2d-9e5f-6a7b8c9d0e1f',
    investment: 'invest_id_123',
    investmentStatus: 1,
    request: '{{request}}',
    nonce: 1594297865000
  })
};

fetch('https://whitebit.com/api/v4/main-account/smart-flex/investments', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://whitebit.com/api/v4/main-account/smart-flex/investments",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'limit' => 100,
    'offset' => 0,
    'ticker' => 'USDT',
    'plan' => '8f2e9d3c-1a4b-4c2d-9e5f-6a7b8c9d0e1f',
    'investment' => 'invest_id_123',
    'investmentStatus' => 1,
    'request' => '{{request}}',
    'nonce' => 1594297865000
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "X-TXC-APIKEY: <api-key>",
    "X-TXC-PAYLOAD: <api-key>",
    "X-TXC-SIGNATURE: <api-key>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://whitebit.com/api/v4/main-account/smart-flex/investments"

	payload := strings.NewReader("{\n  \"limit\": 100,\n  \"offset\": 0,\n  \"ticker\": \"USDT\",\n  \"plan\": \"8f2e9d3c-1a4b-4c2d-9e5f-6a7b8c9d0e1f\",\n  \"investment\": \"invest_id_123\",\n  \"investmentStatus\": 1,\n  \"request\": \"{{request}}\",\n  \"nonce\": 1594297865000\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("X-TXC-APIKEY", "<api-key>")
	req.Header.Add("X-TXC-PAYLOAD", "<api-key>")
	req.Header.Add("X-TXC-SIGNATURE", "<api-key>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://whitebit.com/api/v4/main-account/smart-flex/investments")
  .header("X-TXC-APIKEY", "<api-key>")
  .header("X-TXC-PAYLOAD", "<api-key>")
  .header("X-TXC-SIGNATURE", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"limit\": 100,\n  \"offset\": 0,\n  \"ticker\": \"USDT\",\n  \"plan\": \"8f2e9d3c-1a4b-4c2d-9e5f-6a7b8c9d0e1f\",\n  \"investment\": \"invest_id_123\",\n  \"investmentStatus\": 1,\n  \"request\": \"{{request}}\",\n  \"nonce\": 1594297865000\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://whitebit.com/api/v4/main-account/smart-flex/investments")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["X-TXC-APIKEY"] = '<api-key>'
request["X-TXC-PAYLOAD"] = '<api-key>'
request["X-TXC-SIGNATURE"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"limit\": 100,\n  \"offset\": 0,\n  \"ticker\": \"USDT\",\n  \"plan\": \"8f2e9d3c-1a4b-4c2d-9e5f-6a7b8c9d0e1f\",\n  \"investment\": \"invest_id_123\",\n  \"investmentStatus\": 1,\n  \"request\": \"{{request}}\",\n  \"nonce\": 1594297865000\n}"

response = http.request(request)
puts response.read_body

{
  "data": [
    {
      "id": "inv_7e2d9c3b-1a4b-4c2d-9e5f-6a7b8c9d0e1f",
      "planId": "8f2e9d3c-1a4b-4c2d-9e5f-6a7b8c9d0e1f",
      "currency": "USDT",
      "invested": "1500.75",
      "withAutoReinvest": true,
      "status": 1,
      "createdAt": 1640995200,
      "updatedAt": 1641081600
    }
  ],
  "limit": 100,
  "offset": 0
}

{
  "code": 0,
  "message": "Validation failed",
  "errors": {
    "ticker": [
      "The selected ticker is invalid."
    ],
    "plan": [
      "The selected plan is invalid."
    ],
    "investment": [
      "The selected investment is invalid."
    ],
    "investmentStatus": [
      "The selected investment status is invalid."
    ]
  }
}