Add initial project structure with core functionality

- Created a new Go module named 'teleport' for secure port forwarding.
- Added essential files including .gitignore, LICENSE, and README.md with project details.
- Implemented configuration management with YAML support in config package.
- Developed core client and server functionalities for handling port forwarding.
- Introduced DNS server capabilities and integrated logging with sanitization.
- Established rate limiting and metrics tracking for performance monitoring.
- Included comprehensive tests for core components and functionalities.
- Set up CI workflows for automated testing and release management using Gitea actions.

pkg/ratelimit/ratelimit.go

@@ -0,0 +1,89 @@
+package ratelimit
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+// RateLimiter implements a token bucket rate limiter
+type RateLimiter struct {
+	requestsPerSecond int
+	burstSize         int
+	windowSize        time.Duration
+	tokens            int
+	lastRefill        time.Time
+	mutex             sync.Mutex
+}
+
+// NewRateLimiter creates a new rate limiter
+func NewRateLimiter(requestsPerSecond, burstSize int, windowSize time.Duration) *RateLimiter {
+	return &RateLimiter{
+		requestsPerSecond: requestsPerSecond,
+		burstSize:         burstSize,
+		tokens:            burstSize,
+		lastRefill:        time.Now(),
+		windowSize:        windowSize,
+	}
+}
+
+// Allow checks if a request is allowed under the rate limit
+func (rl *RateLimiter) Allow() bool {
+	rl.mutex.Lock()
+	defer rl.mutex.Unlock()
+
+	now := time.Now()
+
+	// Calculate tokens to add based on time elapsed
+	elapsed := now.Sub(rl.lastRefill)
+	tokensToAdd := int(elapsed.Seconds() * float64(rl.requestsPerSecond))
+
+	if tokensToAdd > 0 {
+		rl.tokens += tokensToAdd
+		if rl.tokens > rl.burstSize {
+			rl.tokens = rl.burstSize
+		}
+		rl.lastRefill = now
+	}
+
+	// Check if we have tokens available
+	if rl.tokens > 0 {
+		rl.tokens--
+		return true
+	}
+
+	return false
+}
+
+// AllowWithContext checks if a request is allowed with context cancellation
+func (rl *RateLimiter) AllowWithContext(ctx context.Context) bool {
+	select {
+	case <-ctx.Done():
+		return false
+	default:
+		return rl.Allow()
+	}
+}
+
+// Wait blocks until a request is allowed
+func (rl *RateLimiter) Wait(ctx context.Context) error {
+	for {
+		if rl.Allow() {
+			return nil
+		}
+
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-time.After(rl.windowSize / time.Duration(rl.requestsPerSecond)):
+			// Wait for next token
+		}
+	}
+}
+
+// GetStats returns current rate limiter statistics
+func (rl *RateLimiter) GetStats() (tokens int, lastRefill time.Time) {
+	rl.mutex.Lock()
+	defer rl.mutex.Unlock()
+	return rl.tokens, rl.lastRefill
+}