Golang招聘：Let's Encrypt招聘初级或高级软件工程师（远程工作）

// 从招聘要求看，这是一个典型的Go语言基础设施开发岗位
// 主要涉及Boulder（ACME服务器）和Pebble（测试工具）的维护开发

// 示例：类似Boulder项目中可能涉及的Go代码结构
package main

import (
    "context"
    "crypto/x509"
    "encoding/json"
    "fmt"
    "log"
    "net/http"
    "time"
)

// ACME证书请求结构
type CertificateRequest struct {
    Domain     string    `json:"domain"`
    PublicKey  []byte    `json:"publicKey"`
    ExpiryTime time.Time `json:"expiryTime"`
}

// Boulder风格的证书颁发服务示例
type CertificateAuthority struct {
    storage StorageBackend
    policy  PolicyEngine
}

func (ca *CertificateAuthority) IssueCertificate(ctx context.Context, req *CertificateRequest) (*x509.Certificate, error) {
    // 验证域名所有权
    if err := ca.policy.ValidateDomain(req.Domain); err != nil {
        return nil, fmt.Errorf("domain validation failed: %w", err)
    }
    
    // 创建证书模板
    template := &x509.Certificate{
        SerialNumber: generateSerial(),
        Subject:      pkix.Name{CommonName: req.Domain},
        NotBefore:    time.Now(),
        NotAfter:     req.ExpiryTime,
        DNSNames:     []string{req.Domain},
    }
    
    // 颁发证书
    certDER, err := x509.CreateCertificate(
        rand.Reader,
        template,
        ca.rootCert,
        req.PublicKey,
        ca.privateKey,
    )
    if err != nil {
        return nil, fmt.Errorf("failed to create certificate: %w", err)
    }
    
    // 存储证书记录
    certRecord := &CertificateRecord{
        SerialNumber: template.SerialNumber.String(),
        Domain:       req.Domain,
        IssuedAt:     time.Now(),
        Certificate:  certDER,
    }
    
    if err := ca.storage.StoreCertificate(ctx, certRecord); err != nil {
        return nil, fmt.Errorf("failed to store certificate: %w", err)
    }
    
    return x509.ParseCertificate(certDER)
}

// ACME API端点处理示例
func (ca *CertificateAuthority) HandleACMERequest(w http.ResponseWriter, r *http.Request) {
    var req CertificateRequest
    if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
        http.Error(w, "invalid request", http.StatusBadRequest)
        return
    }
    
    cert, err := ca.IssueCertificate(r.Context(), &req)
    if err != nil {
        log.Printf("certificate issuance failed: %v", err)
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }
    
    response := map[string]interface{}{
        "certificate": cert.Raw,
        "serial":      cert.SerialNumber.String(),
        "expires":     cert.NotAfter.Format(time.RFC3339),
    }
    
    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(response)
}

// 单元测试示例（招聘要求中提到需要测试经验）
func TestCertificateIssuance(t *testing.T) {
    ca := &CertificateAuthority{
        storage: mockStorage{},
        policy:  mockPolicy{},
    }
    
    req := &CertificateRequest{
        Domain:     "example.com",
        PublicKey:  testPublicKey,
        ExpiryTime: time.Now().Add(90 * 24 * time.Hour),
    }
    
    cert, err := ca.IssueCertificate(context.Background(), req)
    if err != nil {
        t.Fatalf("expected no error, got %v", err)
    }
    
    if cert.Subject.CommonName != "example.com" {
        t.Errorf("expected CN=example.com, got %s", cert.Subject.CommonName)
    }
    
    if cert.NotAfter.Sub(cert.NotBefore) != 90*24*time.Hour {
        t.Errorf("incorrect certificate validity period")
    }
}

// 并发处理示例（处理大规模证书请求）
func (ca *CertificateAuthority) ProcessBatchRequests(ctx context.Context, requests []CertificateRequest) []CertificateResult {
    results := make([]CertificateResult, len(requests))
    var wg sync.WaitGroup
    
    for i, req := range requests {
        wg.Add(1)
        go func(idx int, req CertificateRequest) {
            defer wg.Done()
            
            cert, err := ca.IssueCertificate(ctx, &req)
            results[idx] = CertificateResult{
                Certificate: cert,
                Error:       err,
            }
        }(i, req)
    }
    
    wg.Wait()
    return results
}

// 内存安全解析器示例（招聘中提到正在开发的项目）
type SafeDNSResolver struct {
    cache   *sync.Map
    timeout time.Duration
}

func (r *SafeDNSResolver) Resolve(ctx context.Context, domain string) ([]net.IP, error) {
    // 使用内存安全的方式处理DNS解析
    if cached, ok := r.cache.Load(domain); ok {
        return cached.([]net.IP), nil
    }
    
    ctx, cancel := context.WithTimeout(ctx, r.timeout)
    defer cancel()
    
    ips, err := net.DefaultResolver.LookupIPAddr(ctx, domain)
    if err != nil {
        return nil, err
    }
    
    result := make([]net.IP, len(ips))
    for i, ip := range ips {
        result[i] = ip.IP
    }
    
    r.cache.Store(domain, result)
    return result, nil
}

func main() {
    // 启动ACME服务器
    ca := &CertificateAuthority{
        storage: NewPostgresStorage(),
        policy:  NewDomainPolicy(),
    }
    
    mux := http.NewServeMux()
    mux.HandleFunc("/acme/new-cert", ca.HandleACMERequest)
    mux.HandleFunc("/acme/revoke", ca.HandleRevocationRequest)
    
    server := &http.Server{
        Addr:         ":8080",
        Handler:      mux,
        ReadTimeout:  10 * time.Second,
        WriteTimeout: 30 * time.Second,
    }
    
    log.Println("Starting ACME server on :8080")
    if err := server.ListenAndServe(); err != nil {
        log.Fatal(err)
    }
}

这个岗位需要处理：

1. 并发处理 - 大规模证书颁发需要高效的goroutine管理
2. 密码学操作 - 使用crypto/x509等标准库
3. API设计 - 实现ACME协议端点
4. 测试驱动 - 单元测试和集成测试
5. 内存安全 - 避免内存泄漏和安全漏洞

技术栈包括：Go标准库、HTTP服务器、数据库交互、密码学操作、测试框架。代码需要注重错误处理、资源管理和性能优化。