How to access to OpenAI API with Golang

main.go

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
)

type OpenAIRequest struct {
	Model       string    `json:"model"`
	Messages    []Message `json:"messages"`
	Temperature float64   `json:"temperature"`
}
type Message struct {
	Role    string `json:"role"`
	Content string `json:"content"`
}

type OpenAIResponse struct {
	ID      string `json:"id"`
	Object  string `json:"object"`
	Created int    `json:"created"`
	Model   string `json:"model"`
	Usage   struct {
		PromptTokens     int `json:"prompt_tokens"`
		CompletionTokens int `json:"completion_tokens"`
		TotalTokens      int `json:"total_tokens"`
	} `json:"usage"`
	Choices []struct {
		Message      Message `json:"message"`
		Logprobs     any     `json:"logprobs"`
		FinishReason string  `json:"finish_reason"`
		Index        int     `json:"index"`
	} `json:"choices"`
	Error Error `json:"error"`
}

type Error struct {
	Message string `json:"message"`
	Type    string `json:"type"`
	Param   any    `json:"param"`
	Code    any    `json:"code"`
}

func callOpenAI(data OpenAIRequest) (OpenAIResponse, error) {
	// Generated by curl-to-Go: https://mholt.github.io/curl-to-go

	// curl https://api.openai.com/v1/chat/completions \
	//   -H "Content-Type: application/json" \
	//   -H "Authorization: Bearer $OPENAI_API_KEY" \
	//   -d '{
	//      "model": "gpt-3.5-turbo",
	//      "messages": [{"role": "user", "content": "Say this is a test!"}],
	//      "temperature": 0.7
	//    }'

	payloadBytes, err := json.Marshal(data)
	if err != nil {
		return OpenAIResponse{}, err
	}
	body := bytes.NewReader(payloadBytes)

	req, err := http.NewRequest("POST", "https://api.openai.com/v1/chat/completions", body)
	if err != nil {
		return OpenAIResponse{}, err
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", os.ExpandEnv("Bearer $OPENAI_API_KEY"))

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return OpenAIResponse{}, err
	}
	defer resp.Body.Close()

	var iaResp OpenAIResponse
	err = json.NewDecoder(resp.Body).Decode(&iaResp)
	return iaResp, err
}

func main() {
	data := OpenAIRequest{
		Model:       "gpt-3.5-turbo",
		Messages:    []Message{{Role: "user", Content: "Say this is a test!"}},
		Temperature: 0.7,
	}

	resp, err := callOpenAI(data)
	if err != nil {
		panic(err)
	}

	fmt.Printf("%+v\n", resp)
}