X-Forwarded-For: <client ip>, <proxy1 ip>, <proxy2 ip> 

http {
    # 下面三行为重点, 添加后就可以获取到客户端真实 IP
    set_real_ip_from 0.0.0.0/0;
    real_ip_header X-Forwarded-For;
    real_ip_recursive on;

    # 下面三行为常见反向代理传递真实客户端 IP 的配置
    # 配置在 http{} 中, 则全局应用在下面的所有 server 中
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}

import (
    "fmt"
    "net"
    "net/http"
    "strings"
)

// X-Forwarded-For (XFF) 在客户端访问服务器的过程中如果需要经过 HTTP 代理或者负载均衡服务器,
// 可以被用来获取最初发起请求的客户端的 IP 地址, 这个消息首部成为事实上的标准.
var xForwardedForKeys = [...]string{"X-Forwarded-For", "x-forwarded-for", "X-FORWARDED-FOR"}

// XRealIP nginx 反向代理服务 IP
var xRealIPKeys = [...]string{"X-Real-IP", "X-Real-Ip", "x-real-ip", "X-REAL-IP"}

// GetClientIP 获取客户端 ip
func GetClientIP(r *http.Request) (ip string) {
    // X-Forwarded-For: <client>, <proxy1>, <proxy2>
    for _, xForwardedForKey := range xForwardedForKeys {
        xForwardedFor := strings.TrimSpace(r.Header.Get(xForwardedForKey))
        if len(xForwardedFor) > 0 {
            xForwardedFors := strings.Split(xForwardedFor, ",")
            ip = strings.TrimSpace(xForwardedFors[0])
            if len(ip) > 0 {
                return
            }
            break
        }
    }

    for _, xRealIPKey := range xRealIPKeys {
        ip = strings.TrimSpace(r.Header.Get(xRealIPKey))
        if len(ip) > 0 {
            return
        }
    }

    // 兜底直接使用 client 请求的 ip 地址
    ip, _, _ = net.SplitHostPort(r.RemoteAddr)
    return
}