feat: add support for gpt4 (#6)

Author: ayush6624

README.md

@@ -7,6 +7,7 @@ Go-ChatGPT is an open-source GoLang client for ChatGPT, a large language model t
 - [x] Easy-to-use GoLang client for ChatGPT
 - [x] Sends text to ChatGPT and receives a response
 - [x] Support custom model and parameters
+- [x] Supports GPT3.5 and GPT4 models 
 
 
 ## Installation

chat.go

@@ -14,6 +14,10 @@ type ChatGPTModel string
 const (
 	GPT35Turbo     ChatGPTModel = "gpt-3.5-turbo"
 	GPT35Turbo0301 ChatGPTModel = "gpt-3.5-turbo-0301"
+	GPT4           ChatGPTModel = "gpt-4"
+	GPT4_0314      ChatGPTModel = "gpt-4-0314"
+	GPT4_32k       ChatGPTModel = "gpt-4-32k"
+	GPT4_32k_0314  ChatGPTModel = "gpt-4-32k-0314"
 )
 
 type ChatGPTModelRole string
@@ -139,7 +143,7 @@ func validate(req *ChatCompletionRequest) error {
 		return chatgpt_errors.ErrNoMessages
 	}
 
-	if req.Model != GPT35Turbo && req.Model != GPT35Turbo0301 {
+	if req.Model != GPT35Turbo && req.Model != GPT35Turbo0301 && req.Model != GPT4 && req.Model != GPT4_0314 && req.Model != GPT4_32k && req.Model != GPT4_32k_0314 {
 		return chatgpt_errors.ErrInvalidModel
 	}
 

examples/main.go

@@ -26,7 +26,7 @@ func main() {
 	log.Println(string(a))
 
 	res, err = c.Send(ctx, &chatgpt.ChatCompletionRequest{
-		Model: chatgpt.GPT35Turbo,
+		Model: chatgpt.GPT4,
 		Messages: []chatgpt.ChatMessage{
 			{
 				Role: chatgpt.ChatGPTModelRoleSystem,