go-yfinance

README

go-yfinance

Unofficial Go port of the popular Python library yfinance.

This project is a Go implementation based on the logic of yfinance. It aims to provide a native Go experience (rewrite) while respecting the original API structure.

Features

• TLS Fingerprint Spoofing: Uses CycleTLS to bypass Yahoo's bot detection with Chrome JA3 fingerprint
• Automatic Authentication: Cookie/Crumb management with CSRF fallback for EU users
• Thread-Safe: Concurrent-safe client and configuration
• Comprehensive Error Handling: Typed errors with proper Go error wrapping

Installation

go get github.com/wnjoon/go-yfinance

Quick Start

package main

import (
    "fmt"
    "log"

    "github.com/wnjoon/go-yfinance/pkg/models"
    "github.com/wnjoon/go-yfinance/pkg/ticker"
)

func main() {
    // Create a ticker
    t, err := ticker.New("AAPL")
    if err != nil {
        log.Fatal(err)
    }
    defer t.Close()

    // Get current quote
    quote, err := t.Quote()
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("AAPL: $%.2f (%+.2f%%)\n",
        quote.RegularMarketPrice,
        quote.RegularMarketChangePercent)

    // Get historical data
    bars, err := t.History(models.HistoryParams{
        Period:   "1mo",
        Interval: "1d",
    })
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("\nLast 5 days:\n")
    start := len(bars) - 5
    if start < 0 {
        start = 0
    }
    for _, bar := range bars[start:] {
        fmt.Printf("%s: O=%.2f H=%.2f L=%.2f C=%.2f V=%d\n",
            bar.Date.Format("2006-01-02"),
            bar.Open, bar.High, bar.Low, bar.Close, bar.Volume)
    }

    // Get company info
    info, err := t.Info()
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("\nCompany: %s\n", info.LongName)
    fmt.Printf("Sector: %s\n", info.Sector)
    fmt.Printf("Industry: %s\n", info.Industry)
    fmt.Printf("Market Cap: $%d\n", info.MarketCap)
}

Rate Limiting

⚠️ Note: This library does not enforce rate limiting internally. Yahoo Finance may block IP addresses with excessive request volume. To avoid 429 Too Many Requests errors, manage concurrency on the client side using worker pools, semaphores, or request throttling.

Configuration

import "github.com/wnjoon/go-yfinance/pkg/config"

// Global configuration
cfg := config.Get()
cfg.SetTimeout(60 * time.Second).
    SetMaxRetries(5).
    SetDebug(true)

// Or create custom config
customCfg := config.NewDefault().
    SetProxy("http://proxy:8080").
    EnableCache(10 * time.Minute)

Project Structure

go-yfinance/
├── cmd/example/              # Usage examples
├── internal/
│   └── endpoints/            # Yahoo Finance API endpoints
├── pkg/
│   ├── client/               # HTTP client with TLS fingerprint
│   │   ├── client.go         # CycleTLS-based client
│   │   ├── auth.go           # Cookie/Crumb authentication
│   │   └── errors.go         # Error types
│   ├── config/               # Configuration management
│   ├── ticker/               # Ticker data (Phase 1+)
│   └── models/               # Data models (Phase 1+)
└── README.md

Dependencies

• CycleTLS - TLS fingerprint spoofing
• gorilla/websocket - WebSocket client for real-time streaming

Legal & License

go-yfinance is distributed under the Apache Software License 2.0. See the LICENSE file in the repository for details.

Disclaimer

Please read this carefully before using this library.

1. Unofficial API: This library is not affiliated with, endorsed by, or connected to Yahoo! Finance. It wraps unofficial API endpoints intended for web browser consumption.

2. Research & Educational Use: This library is intended for research and educational purposes.

3. Terms of Service: Use of this library must comply with Yahoo!'s Terms of Service. Users are solely responsible for ensuring their usage is compliant.

4. Risk of Blocking: Since this library relies on unofficial methods, Yahoo! Finance may change their API structure or block IP addresses making excessive requests at any time without notice.

5. No Warranty: This software is provided "as is", without warranty of any kind, express or implied. The authors shall not be held liable for any damages or legal issues arising from the use of this software.

Credits

This project is a Go implementation based on the logic of yfinance. Special thanks to Ran Aroussi and all contributors of the original project for their excellent work.