Golang中如何将HTTP请求重定向到HTTPS：解决"Client sent an HTTP request to an HTTPS server"错误

在Go中处理HTTP到HTTPS重定向，可以通过以下方式实现自定义处理程序：

package main

import (
    "net/http"
    "strings"
)

func redirectToHTTPS(w http.ResponseWriter, r *http.Request) {
    // 构建HTTPS URL
    host := r.Host
    if strings.Contains(host, ":") {
        host = strings.Split(host, ":")[0]
    }
    
    httpsURL := "https://" + host + ":443" + r.URL.Path
    if r.URL.RawQuery != "" {
        httpsURL += "?" + r.URL.RawQuery
    }
    
    // 执行301永久重定向
    http.Redirect(w, r, httpsURL, http.StatusMovedPermanently)
}

func main() {
    // HTTP服务器监听80端口
    go func() {
        http.HandleFunc("/", redirectToHTTPS)
        http.ListenAndServe(":80", nil)
    }()
    
    // HTTPS服务器监听443端口
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("HTTPS连接成功"))
    })
    
    // 启动HTTPS服务器（需要证书文件）
    http.ListenAndServeTLS(":443", "server.crt", "server.key", nil)
}

对于更细粒度的控制，可以使用自定义服务器配置：

package main

import (
    "crypto/tls"
    "net/http"
    "time"
)

func main() {
    // 创建自定义HTTP服务器处理重定向
    httpServer := &http.Server{
        Addr: ":80",
        Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            target := "https://" + r.Host + r.URL.Path
            if r.URL.RawQuery != "" {
                target += "?" + r.URL.RawQuery
            }
            http.Redirect(w, r, target, http.StatusPermanentRedirect)
        }),
        ReadTimeout:  5 * time.Second,
        WriteTimeout: 10 * time.Second,
    }
    
    // 创建HTTPS服务器
    httpsServer := &http.Server{
        Addr: ":443",
        Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            w.Write([]byte("安全连接已建立"))
        }),
        TLSConfig: &tls.Config{
            MinVersion: tls.VersionTLS12,
        },
        ReadTimeout:  5 * time.Second,
        WriteTimeout: 10 * time.Second,
    }
    
    // 启动HTTP重定向服务器
    go httpServer.ListenAndServe()
    
    // 启动HTTPS服务器
    httpsServer.ListenAndServeTLS("server.crt", "server.key")
}

如果需要在单个端口中处理混合协议，可以使用TLS嗅探：

package main

import (
    "bytes"
    "crypto/tls"
    "net"
    "net/http"
)

func handleConn(conn net.Conn) {
    defer conn.Close()
    
    // 读取前几个字节判断是否为TLS握手
    buf := make([]byte, 1)
    conn.Read(buf)
    
    if buf[0] == 0x16 { // TLS握手开始标志
        // 重建连接进行TLS处理
        tlsConn := tls.Server(&bufferedConn{
            Conn:   conn,
            buffer: append(buf, make([]byte, 4095)...),
        }, &tls.Config{
            Certificates: []tls.Certificate{loadCertificate()},
        })
        
        http.Serve(tlsConn, http.HandlerFunc(httpsHandler))
    } else {
        // 处理HTTP重定向
        http.Serve(&bufferedConn{
            Conn:   conn,
            buffer: append(buf, make([]byte, 4095)...),
        }, http.HandlerFunc(redirectHandler))
    }
}

type bufferedConn struct {
    net.Conn
    buffer []byte
    offset int
}

func (bc *bufferedConn) Read(p []byte) (n int, err error) {
    if bc.offset < len(bc.buffer) {
        n = copy(p, bc.buffer[bc.offset:])
        bc.offset += n
        return n, nil
    }
    return bc.Conn.Read(p)
}

func redirectHandler(w http.ResponseWriter, r *http.Request) {
    http.Redirect(w, r, "https://"+r.Host+r.RequestURI, http.StatusMovedPermanently)
}

func httpsHandler(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("安全HTTPS连接"))
}

这些示例展示了在Go中处理"Client sent an HTTP request to an HTTPS server"错误的不同方法，通过重定向HTTP请求到HTTPS端点来解决协议不匹配问题。