Reasoning · language

Use Claude 3.5 Sonnet (Thinking) with Go

Updated 2026-05-21 · By XALEN

How to use Claude 3.5 Sonnet (Thinking) (Reasoning, ~500B) with Go. Install, authenticate, and make your first API call in minutes. Working code example included.

Model
Claude 3.5 Sonnet (Thinking)
~500B · 200K context · $0.03 input
Framework
Go
language · go get github.com/sashabaranov/go-openai

1. Install

go get github.com/sashabaranov/go-openai

2. Code

package main

import (
    "context"
    "fmt"
    openai "github.com/sashabaranov/go-openai"
)

func main() {
    config := openai.DefaultConfig("xln_test_YOUR_KEY")
    config.BaseURL = "https://api.xalen.io/v1"
    client := openai.NewClientWithConfig(config)

    resp, _ := client.CreateChatCompletion(context.Background(),
        openai.ChatCompletionRequest{
            Model: "claude-3-5-sonnet-thinking",
            Messages: []openai.ChatCompletionMessage{
                {Role: "user", Content: "Hello from Go!"},
            },
        })
    fmt.Println(resp.Choices[0].Message.Content)
}

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Last updated: 2026-05-21