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Claude Code in VSCode with Go: A Beginner's Guide

1. Overview​

Claude Code is an AI-powered coding assistant that integrates directly into VSCode, allowing you to build, refactor, and debug software by having natural conversations. If you are new to Claude Code or to the Go programming language, this guide will walk you through setting up Claude Code in VSCode and building your first Go REST API project from scratch.

In this guide you will learn:

  • How to install and authenticate Claude Code in VSCode
  • How to open Claude Code and understand its interface
  • How to write effective prompts that Claude can act on
  • How to build a complete Go REST API with CRUD operations
  • How to iterate and improve your code using Claude Code's interactive features
  • Common beginner workflows: creating files, reviewing diffs, testing your code

By the end, you will have a working Go REST API running in VSCode and the confidence to tackle larger projects with Claude Code's help.

No prior experience with Claude Code, VSCode, or Go is assumed. You should have basic comfort with the command line (cd, ls, mkdir).

2. Prerequisites​

Before starting, make sure you have:

  • VSCode — Version 1.98.0 or later. Download from code.visualstudio.com
  • Node.js — Version 18 or later (required for Claude Code CLI). Check with node --version; download from nodejs.org
  • Go — Version 1.21 or later. Check with go version; download from go.dev
  • Git — For version control (recommended). Check with git --version
  • Claude Account — An active account on claude.ai with a Pro or Max plan
  • Administrator or sudo access — To install global npm packages (Claude Code CLI)

3. Key Concepts​

Claude Code Basics​

Claude Code is a VSCode extension that connects you to Claude, an advanced AI assistant. Unlike traditional coding assistants that only suggest snippets, Claude Code can:

  • Understand your entire project and make multi-file edits
  • Create a plan before making changes so you can review and approve
  • Generate unit tests, documentation, and refactors
  • Adapt based on your feedback in real-time
  • Reference your project context, errors, and terminal output

Go REST API Basics​

A REST API (Representational State Transfer Application Programming Interface) is a way for clients (like web browsers or mobile apps) to communicate with a server over HTTP. For example:

  • GET /tasks — retrieve all tasks
  • POST /tasks — create a new task
  • GET /tasks/1 — retrieve task with ID 1
  • PUT /tasks/1 — update task 1
  • DELETE /tasks/1 — delete task 1

Go is a compiled programming language well-suited to building fast, efficient APIs. We will use only the Go standard library (no external frameworks), which means fewer dependencies and easier setup for learning.

How Claude Code Works with Your Code​

  1. You open Claude Code and type a prompt describing what you want
  2. Claude analyzes your project and generates a plan showing exactly which files it will create/modify
  3. You review the plan and approve or request changes
  4. Claude makes the changes, showing inline diffs in your editor
  5. You review each diff, accept or reject it, and the files are updated
  6. You test your code and give Claude feedback if something needs fixing

4. Step-by-Step Instructions​

Step 1 — Install the Claude Code Extension​

  1. Open VSCode
  2. Press Ctrl+Shift+X (Windows/Linux) or Cmd+Shift+X (Mac) to open the Extensions sidebar
  3. In the search box, type: Claude Code
  4. Find the extension published by Anthropic (the official one)
  5. Click the Install button
  6. VSCode may prompt you to reload. Click Reload or run Developer: Reload Window from the Command Palette (Ctrl+Shift+P)

Verification: After installation, open any file in your editor. You should see a ✦ spark icon in the top-right corner of the editor toolbar. If you see it, the extension is installed correctly.

Step 2 — Install Claude Code CLI via npm​

Claude Code uses a command-line tool that manages the connection to Claude's API. Install it globally:

Open a terminal (or VSCode's integrated terminal with Ctrl+`) and run:

npm install -g @anthropic-ai/claude-code

Verify it installed successfully:

claude --version

Expected output (version may differ):

@anthropic-ai/claude-code/0.1.0

If you get a "command not found" error, Node.js may not be in your PATH. Restart your terminal or VSCode and try again.

Step 3 — Authenticate Claude Code​

Authentication securely connects Claude Code to your Claude account. Run:

claude login

This opens a browser window with an OAuth login flow. Sign in with your Claude account credentials. Once authenticated, you will see a confirmation in your terminal, and you are ready to use Claude Code.

Step 4 — Create Your First Go Project Folder​

In a terminal, create a new directory for your project:

mkdir task-api
cd task-api
go mod init github.com/yourname/task-api

The go mod init command creates a go.mod file that tracks your project's dependencies (in this case, there will be none because we are using only the standard library).

Then open the folder in VSCode:

code .

This launches a new VSCode window with your project folder open.

Step 5 — Open Claude Code and Give Your First Prompt​

In VSCode, open any file or create a new one. Click the ✦ spark icon in the top-right editor toolbar. A Claude Code panel will open on the right side of your editor.

In the chat input field at the bottom of the panel, paste the following prompt:

Create a simple REST API in Go for managing tasks. The API should support CRUD operations 
(Create, Read, Update, Delete) for tasks. Each task should have an ID, title, description, 
and completed status. Use only the Go standard library (no external frameworks). Include a 
main.go, handlers.go, and models.go file. Add a README.md explaining how to run the project.

Press Enter or click Send.

Claude will analyze your request and display a plan showing which files it will create or modify. Review the plan carefully.

Step 6 — Review and Approve Claude's Plan​

Before Claude makes any changes, it shows you the plan. For this prompt, you should see something like:

Plan:
1. Create main.go — HTTP server setup and request routing
2. Create models.go — Task struct definition and in-memory store
3. Create handlers.go — HTTP handler functions for CRUD operations
4. Create README.md — Documentation

Click the Approve button (or type "approve" in the chat) to proceed. Claude will now create the files.

Step 7 — Review Inline Diffs​

As Claude creates each file, the content appears as an inline diff in your editor. The diff shows:

  • Green highlighted lines: new content being added
  • Red highlighted lines: existing content being removed

For each diff, you have two options:

  • ✓ (checkmark) — Accept this change
  • ✗ (X) — Reject this change

You can also:

  • Accept All — Accept all diffs for the file at once
  • Reject All — Reject all diffs for the file at once

For your first project, review each diff briefly to understand what Claude is creating, then accept all of them.

Step 8 — Explore Your Generated Project​

After Claude finishes, open the Explorer panel in VSCode (Ctrl+Shift+E) and examine the files:

task-api/
├── go.mod
├── main.go
├── models.go
├── handlers.go
└── README.md

Open each file to see the code. Take a moment to read through:

  • main.go — The entry point, where the HTTP server starts
  • models.go — The Task struct and the in-memory task store
  • handlers.go — The handler functions that process HTTP requests
  • README.md — Instructions for running the API

Understanding what Claude generated will help you write better prompts for improvements.

Step 9 — Run Your API​

Open the integrated terminal in VSCode by pressing Ctrl+`. Make sure you are in the task-api directory, then run:

go run .

Expected output:

Server starting on :8080

This starts your Go REST API server listening on port 8080 of your local machine. The server will keep running until you stop it (Ctrl+C).

Step 10 — Test Your API​

Open a new terminal window or tab (keep the server running in the first terminal). Test the API with curl:

# Create a task
curl -X POST http://localhost:8080/tasks \
  -H "Content-Type: application/json" \
  -d '{"title":"Learn Claude Code","description":"Build a Go API"}'

Expected output (a task ID will be returned):

{"id":1,"title":"Learn Claude Code","description":"Build a Go API","completed":false}

List all tasks:

curl http://localhost:8080/tasks

Expected output:

[{"id":1,"title":"Learn Claude Code","description":"Build a Go API","completed":false}]

Get a specific task:

curl http://localhost:8080/tasks/1

Update a task:

curl -X PUT http://localhost:8080/tasks/1 \
  -H "Content-Type: application/json" \
  -d '{"title":"Learn Claude Code","description":"Build a Go API","completed":true}'

Delete a task:

curl -X DELETE http://localhost:8080/tasks/1

Congratulations! You have successfully built and tested a working REST API.

5. Practical Examples​

Example 1 — Adding Input Validation​

After testing the basic API, you might notice that you can create tasks with empty titles. Let's add validation. In the Claude Code chat, type:

Add input validation to the POST and PUT endpoints. Return 400 Bad Request with descriptive 
error messages if the title is empty or the description is missing.

Claude will review your code, create a plan (likely modifying handlers.go and models.go), and show you the diffs. Review and approve them. Test with:

curl -X POST http://localhost:8080/tasks \
  -H "Content-Type: application/json" \
  -d '{"title":"","description":""}'

You should now get a 400 error with a helpful message instead of a task being created.

Example 2 — Adding Unit Tests​

To test your handlers, ask Claude:

Add unit tests for all handler functions in a new file handlers_test.go. Use the standard 
testing package. Include tests for creating, reading, updating, and deleting tasks.

Claude will create handlers_test.go with comprehensive tests. Run them with:

go test -v ./...

Expected output:

=== RUN   TestCreateTask
--- PASS: TestCreateTask (0.01s)
=== RUN   TestGetTasks
--- PASS: TestGetTasks (0.01s)
...
PASS
ok      github.com/yourname/task-api   0.10s

Example 3 — Adding Persistent Storage​

Currently, your tasks are stored in memory and are lost when the server restarts. Ask Claude to persist data:

Replace the in-memory task store with a JSON file for simple persistence. Tasks should be 
saved to a file called tasks.json whenever a task is created, updated, or deleted. Load 
existing tasks from tasks.json on startup.

Claude will modify models.go to add file I/O. After accepting the changes, your tasks will now survive server restarts.

Example 4 — Adding Logging Middleware​

To see what requests are hitting your API, ask Claude:

Add a simple logging middleware that prints the HTTP method, path, status code, and 
response time for every request.

Claude will modify main.go to wrap the handlers with logging. Restart your server and make requests:

go run .

You will now see logs like:

2026-04-10 10:30:45 | POST /tasks | 201 | 1.23ms
2026-04-10 10:30:47 | GET /tasks | 200 | 0.45ms

6. Hands-On Exercises​

Exercise 1 — Describe the Codebase​

  1. Open the Claude Code chat
  2. Ask: "Explain how the task creation flow works, from the HTTP request to the task being stored"
  3. Claude will walk you through the code path
  4. This helps you understand how your API is organized

Exercise 2 — Add a New Feature​

  1. Open the Claude Code chat
  2. Ask: "Add a GET endpoint /stats that returns the total number of tasks and how many are completed"
  3. Review the plan Claude presents
  4. Approve and review the diffs
  5. Test the new endpoint with curl http://localhost:8080/stats

Exercise 3 — Fix a Bug You Introduce​

  1. Intentionally break something in handlers.go (e.g., change a function name)
  2. Try to go run . in the terminal
  3. Copy the error from the terminal
  4. Paste it into Claude Code with: "I got this error: [paste error]. Can you fix it?"
  5. Review Claude's fix and approve it

Exercise 4 — Refactor for Clarity​

  1. Ask Claude: "Refactor the code to move error response writing into a helper function"
  2. Review the plan and accept the changes
  3. Run go test -v ./... to make sure tests still pass

Exercise 5 — Create a Simple Client​

  1. Ask Claude: "Create a simple Go program in a cmd/client directory that calls this API to create a task and retrieve all tasks"
  2. Test it with go run ./cmd/client

7. Troubleshooting​

"Permission denied" when installing Claude Code CLI​

Cause: npm does not have permission to write to the global package directory.

Fix: Use sudo npm install -g @anthropic-ai/claude-code, or configure npm to use a directory you own:

mkdir ~/.npm-global
npm config set prefix '~/.npm-global'
export PATH=~/.npm-global/bin:$PATH
npm install -g @anthropic-ai/claude-code

"claude: command not found" after installation​

Cause: The npm global bin directory is not in your PATH, or you need to restart your terminal.

Fix: Restart your terminal window. If that does not work, run npm config get prefix and check that the output's bin directory is in your PATH.

Claude Code panel does not appear when I click the spark icon​

Cause: The extension did not load properly, or VSCode is not authenticated.

Fix:

  1. Reload VSCode: Ctrl+Shift+P → "Developer: Reload Window"
  2. Make sure Claude Code is installed: Ctrl+Shift+X and search for "Claude Code"
  3. Check that claude login was run and completed successfully

"Server error" or "unauthorized" when sending a prompt​

Cause: Your authentication token expired or is invalid.

Fix: Run claude login again to refresh your authentication.

go run . fails with "package not found"​

Cause: A package import is incorrect, or a package is not installed.

Fix: Run go mod tidy to clean up your go.mod file, then try again. If the error persists, ask Claude to fix the import error.

"Address already in use" when starting the server​

Cause: Another process is already listening on port 8080.

Fix: Either stop the other process, or modify main.go to use a different port (ask Claude to do this for you).

Inline diffs are hard to read​

Cause: This is normal; inline diffs can be visually dense.

Fix: Click on the file in the diff to open it in a split pane view, which is sometimes clearer. You can also click Reject and ask Claude to make smaller, more focused changes.

8. References​

9. Summary​

Key takeaways:

  • Claude Code integrates AI assistance directly into VSCode, helping you write and refactor code faster
  • Installation requires three steps: install the VSCode extension, install the CLI via npm, and authenticate with claude login
  • You interact with Claude by typing natural-language prompts; Claude proposes a plan you review before execution
  • Inline diffs let you see exactly what Claude is changing before accepting
  • Go's standard library is sufficient to build complete REST APIs; no heavy frameworks needed
  • Iterative improvement with Claude is fast: test your code, identify issues, ask Claude to fix or enhance them, and repeat

Next steps:

  • Explore [[git-worktrees-worktrunk-beginner-guide|Git Worktrees with Worktrunk]] to manage feature branches cleanly
  • Ask Claude to add database persistence (SQLite or PostgreSQL) to your API
  • Build a frontend client in a framework of your choice (React, Vue, etc.) that consumes your API
  • Deploy your API to a cloud platform (AWS, Google Cloud, Heroku)
  • Read the Claude Code Deep Dive to learn advanced features like prompt engineering and multi-file refactoring
  • [[git-worktrees-worktrunk-beginner-guide|Git Worktrees with Worktrunk]] — Manage parallel development branches efficiently
  • Linux Permissions Beginner Guide — Understand file permissions for deploying your API to servers
  • Claude Code Deep Dive — Advanced Claude Code workflows, prompt engineering, and optimization

Related Tutorials

  • [[gh-cli-beginner-guide|GitHub CLI Beginner Guide]] — manage repos and PRs from the terminal

  • [[gh-cli-deep-dive|GitHub CLI Deep Dive]] — advanced GitHub workflows for development

  • [[tmux-claude-code-beginner-guide|Tmux + Claude Code Beginner Guide]] — Use Claude Code in tmux for terminal-first workflows

  • [[tmux-claude-code-deep-dive|Tmux + Claude Code Deep Dive]] — Advanced tmux + Claude Code patterns