Model hyperparams with Temperature value 0 is not being respected

[nmanchinn]

Describe the bug
When clients set the model hyperparameters like Temperature to 0, they are being ignored and not sent to OpenAI. This causes LLM to use their default values ( for example, temperature 1 )

To Reproduce
While creating the request set the temperature value to 0

This will send the request to OpenAI as below

"{\"model\":\"gpt-3.5-turbo-0301\",\"messages\":[{\"role\":\"system\",\"content\":\"You are an AI Chatbot. Follow the user's instructions carefully. Respond using markdown. You have a knowledge cutoff of 2021.\"},{\"role\":\"user\",\"content\":\"What are the 3 topics I asked you to write about?\"}],\"max_tokens\":2048,\"stream\":true}"

Expected behavior
Temperature 0 should be sent to openai
"{"model":"gpt-3.5-turbo-0301","messages":[{"role":"system","content":"You are an AI Chatbot. Follow the user's instructions carefully. Respond using markdown. You have a knowledge cutoff of 2021."},{"role":"user","content":"What are the 3 topics I asked you to write about?"}],"max_tokens":2048,"temperature":0,"stream":true}"

**Screenshots/Logs**
This is the the request sent to OpenAI

"{"model":"gpt-3.5-turbo-0301","messages":[{"role":"system","content":"You are an AI Chatbot. Follow the user's instructions carefully. Respond using markdown. You have a knowledge cutoff of 2021."},{"role":"user","content":"What are the 3 topics I asked you to write about?"}],"max_tokens":2048,"stream":true}"

**Environment (please complete the following information):**
 - go-openai version:  v1.11.1
 - Go version:1.20
 - OpenAI API version: v1
 - OS: Ubuntu 20.04

[nmanchinn]

This issue is with the omitempty field tag: https://github.com/sashabaranov/go-openai/blob/master/chat.go#L48

[vvatanabe]

@nmanchinn Thanks for feedback! This problem has already been reported. Please see #9.

[vvatanabe]

This is a duplicate issue with #9, so please discuss it in #9 from now on.