go语言之行--网络编程、http处理流程详情

一、简介

go语言中的网络编程主要通过net包实现，net包提供了网络I/O接口，包括HTTP、TCP/IP、UDP、域名解析和Unix域socket等。和大多数语言一样go可以使用几行代码便可以启动一个服务器，但是得益于goroutine的配合go实现的服务器拥有强大并发处理能力。

二、socket编程

Socket又称"套接字"，应用程序通常通过"套接字"向网络发出请求或者应答网络请求。

socket本质上就是在2台网络互通的电脑之间，架设一个通道，两台电脑通过这个通道来实现数据的互相传递。我们知道网络通信都是基于 ip+port 方能定位到目标的具体机器上的具体服务，操作系统有0-65535个端口，每个端口都可以独立对外提供服务，如果把一个公司比做一台电脑，那公司的总机号码就相当于ip地址，每个员工的分机号就相当于端口，你想找公司某个人，必须先打电话到总机，然后再转分机。

go中socket编程实现起来非常方便，下面是处理流程

服务器端：

监听端口
接受客户端连接
创建goroutine处理连接

客户端：

建立连接
收发数据
关闭连接

服务端示例：

package main

import (

    "fmt"

    "net"

)

func handle(conn net.Conn)  {    //处理连接方法

    defer conn.Close()  //关闭连接

    for{

        buf := make([]byte,)

        n,err := conn.Read(buf)  //读取客户端数据

        if err!=nil {

            fmt.Println(err)

            return

        }

        fmt.Printf("read data size %d msg:%s", n, string(buf[:n]))

        msg := []byte("hello,world\n")

        conn.Write(msg)  //发送数据

    }

}

func main()  {

    fmt.Println("start server....")

    listen,err := net.Listen("tcp","0.0.0.0:3000") //创建监听

    if err != nil{

        fmt.Println("listen failed! msg :" ,err)

        return

    }

    for{

        conn,errs := listen.Accept()  //接受客户端连接

        if errs != nil{

            fmt.Println("accept failed")

            continue

        }

        go handle(conn) //处理连接

    }

}

客户端示例：

package main

import (

    "bufio"

    "fmt"

    "net"

    "os"

    "strings"

)

func main() {

    conn, err := net.Dial("tcp", "127.0.0.1:3000")

    if err != nil {

        fmt.Println("err dialing:", err.Error())

        return

    }

    defer conn.Close()

    inputReader := bufio.NewReader(os.Stdin)

    for {

        str, _ := inputReader.ReadString('\n')

        data := strings.Trim(str, "\n")

        if data == "quit" {   //输入quit退出

            return

        }

        _, err := conn.Write([]byte(data)) //发送数据

        if err != nil {

            fmt.Println("send data error:", err)

            return

        }

        buf := make([]byte,)

        n,err := conn.Read(buf)  //读取服务端端数据

        fmt.Println("from server:", string(buf[:n]))

    }

}

conn示例还提供其他方法：

type Conn interface {

    // Read reads data from the connection.

    // Read can be made to time out and return an Error with Timeout() == true

    // after a fixed time limit; see SetDeadline and SetReadDeadline.

    Read(b []byte) (n int, err error)  //读取连接中数据

    // Write writes data to the connection.

    // Write can be made to time out and return an Error with Timeout() == true

    // after a fixed time limit; see SetDeadline and SetWriteDeadline.

    Write(b []byte) (n int, err error) //发送数据

    // Close closes the connection.

    // Any blocked Read or Write operations will be unblocked and return errors.

    Close() error   //关闭链接

    // LocalAddr returns the local network address.

    LocalAddr() Addr //返回本地连接地址

    // RemoteAddr returns the remote network address.

    RemoteAddr() Addr //返回远程连接的地址

    // SetDeadline sets the read and write deadlines associated

    // with the connection. It is equivalent to calling both

    // SetReadDeadline and SetWriteDeadline.

    //

    // A deadline is an absolute time after which I/O operations

    // fail with a timeout (see type Error) instead of

    // blocking. The deadline applies to all future and pending

    // I/O, not just the immediately following call to Read or

    // Write. After a deadline has been exceeded, the connection

    // can be refreshed by setting a deadline in the future.

    //

    // An idle timeout can be implemented by repeatedly extending

    // the deadline after successful Read or Write calls.

    //

    // A zero value for t means I/O operations will not time out.

    SetDeadline(t time.Time) error //设置链接读取或者写超时时间

    // SetReadDeadline sets the deadline for future Read calls

    // and any currently-blocked Read call.

    // A zero value for t means Read will not time out.

    SetReadDeadline(t time.Time) error //单独设置读取超时时间

    // SetWriteDeadline sets the deadline for future Write calls

    // and any currently-blocked Write call.

    // Even if write times out, it may return n > 0, indicating that

    // some of the data was successfully written.

    // A zero value for t means Write will not time out.

    SetWriteDeadline(t time.Time) error//单独设置写超时时间

}

三、go中HTTP服务处理流程

简介

网络发展，很多网络应用都是构建再 HTTP 服务基础之上。HTTP 协议从诞生到现在，发展从1.0，1.1到2.0也不断再进步。除去细节，理解 HTTP 构建的网络应用只要关注两个端---客户端（clinet）和服务端（server），两个端的交互来自 clinet 的 request，以及server端的response。所谓的http服务器，主要在于如何接受 clinet 的 request，并向client返回response。接收request的过程中，最重要的莫过于路由（router），即实现一个Multiplexer器。Go中既可以使用内置的mutilplexer --- DefautServeMux，也可以自定义。Multiplexer路由的目的就是为了找到处理器函数（handler），后者将对request进行处理，同时构建response。

最后简化的请求处理流程为：

Clinet -> Requests ->  [Multiplexer(router) -> handler  -> Response -> Clinet

因此，理解go中的http服务，最重要就是要理解Multiplexer和handler，Golang中的Multiplexer基于ServeMux结构，同时也实现了Handler接口。

对象说明：

hander函数：具有func(w http.ResponseWriter, r *http.Requests)签名的函数
handler函数: 经过HandlerFunc结构包装的handler函数，它实现了ServeHTTP接口方法的函数。调用handler处理器的ServeHTTP方法时，即调用handler函数本身。
handler对象：实现了Handler接口ServeHTTP方法的结构。

handler处理器和handler对象的差别在于，一个是函数，另外一个是结构，它们都有实现了ServeHTTP方法。很多情况下它们的功能类似，下文就使用统称为handler。

Handler

Golang没有继承，类多态的方式可以通过接口实现。所谓接口则是定义声明了函数签名，任何结构只要实现了与接口函数签名相同的方法，就等同于实现了接口。go的http服务都是基于handler进行处理。

type Handler interface {

    ServeHTTP(ResponseWriter, *Request)

}

任何结构体，只要实现了ServeHTTP方法，这个结构就可以称之为handler对象。ServeMux会使用handler并调用其ServeHTTP方法处理请求并返回响应。

ServeMux

源码部分：

type ServeMux struct {

    mu    sync.RWMutex

    m     map[string]muxEntry

    hosts bool

}

type muxEntry struct {

    explicit bool

    h        Handler

    pattern  string

}

ServeMux结构中最重要的字段为m，这是一个map，key是一些url模式，value是一个muxEntry结构，后者里定义存储了具体的url模式和handler。当然，所谓的ServeMux也实现了ServeHTTP接口，也算是一个handler，不过ServeMux的ServeHTTP方法不是用来处理request和respone，而是用来找到路由注册的handler，后面再做解释。

Server

除了ServeMux和Handler，还有一个结构Server需要了解。从http.ListenAndServe的源码可以看出，它创建了一个server对象，并调用server对象的ListenAndServe方法：

func ListenAndServe(addr string, handler Handler) error {

    server := &Server{Addr: addr, Handler: handler}

    return server.ListenAndServe()

}

查看server的结构如下：

type Server struct {

    Addr         string

    Handler      Handler

    ReadTimeout  time.Duration

    WriteTimeout time.Duration

    TLSConfig    *tls.Config   

    MaxHeaderBytes int

    TLSNextProto map[string]func(*Server, *tls.Conn, Handler)

    ConnState func(net.Conn, ConnState)

    ErrorLog *log.Logger

    disableKeepAlives int32     nextProtoOnce     sync.Once

    nextProtoErr      error

}

server结构存储了服务器处理请求常见的字段。其中Handler字段也保留Handler接口。如果Server接口没有提供Handler结构对象，那么会使用DefautServeMux做multiplexer，后面再做分析。

创建HTTP服务

创建一个http服务，大致需要经历两个过程，首先需要注册路由，即提供url模式和handler函数的映射，其次就是实例化一个server对象，并开启对客户端的监听。

http.HandleFunc("/", indexHandler)

http.ListenAndServe("127.0.0.1:8000", nil)

或

server := &Server{Addr: addr, Handler: handler}

server.ListenAndServe()

示例：

package main

import (

"fmt"

"net/http"

)

func Hello(w http.ResponseWriter, r *http.Request) {

fmt.Println("Hello World.")

fmt.Fprintf(w, "Hello World.\n")

}

func main() {

http.HandleFunc("/", Hello)

err := http.ListenAndServe("0.0.0.0:6000", nil)

if err != nil {

fmt.Println("http listen failed.")

}

}

//curl http://127.0.0.1:6000

// 结果：Hello World

路由注册

net/http包暴露的注册路由的api很简单，http.HandleFunc选取了DefaultServeMux作为multiplexer：

func HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {

    DefaultServeMux.HandleFunc(pattern, handler)

}

DefaultServeMux是ServeMux的一个实例。当然http包也提供了NewServeMux方法创建一个ServeMux实例，默认则创建一个DefaultServeMux：

// NewServeMux allocates and returns a new ServeMux.

func NewServeMux() *ServeMux { return new(ServeMux) }

// DefaultServeMux is the default ServeMux used by Serve.

var DefaultServeMux = &defaultServeMux

var defaultServeMux ServeMux

DefaultServeMux的HandleFunc(pattern, handler)方法实际是定义在ServeMux下的：

// HandleFunc registers the handler function for the given pattern.

func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {

    mux.Handle(pattern, HandlerFunc(handler))

}

HandlerFunc是一个函数类型。同时实现了Handler接口的ServeHTTP方法。使用HandlerFunc类型包装一下路由定义的indexHandler函数，其目的就是为了让这个函数也实现ServeHTTP方法，即转变成一个handler处理器(函数)。

type HandlerFunc func(ResponseWriter, *Request)

// ServeHTTP calls f(w, r).

func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {

    f(w, r)

}

我们最开始写的例子中
http.HandleFunc("/",Indexhandler)
这样 IndexHandler 函数也有了ServeHTTP方法。ServeMux的Handle方法，将会对pattern和handler函数做一个map映射：

func ListenAndServe(addr string, handler Handler) error {

    server := &Server{Addr: addr, Handler: handler}

    return server.ListenAndServe()

}

// ListenAndServe listens on the TCP network address srv.Addr and then

// calls Serve to handle requests on incoming connections.

// Accepted connections are configured to enable TCP keep-alives.

// If srv.Addr is blank, ":http" is used.

// ListenAndServe always returns a non-nil error.

func (srv *Server) ListenAndServe() error {

    addr := srv.Addr

    if addr == "" {

        addr = ":http"

    }

    ln, err := net.Listen("tcp", addr)

    if err != nil {

        return err

    }

    return srv.Serve(tcpKeepAliveListener{ln.(*net.TCPListener)})

}

Server的ListenAndServe方法中，会初始化监听地址Addr，同时调用Listen方法设置监听。最后将监听的TCP对象传入Serve方法：

// Serve accepts incoming connections on the Listener l, creating a

// new service goroutine for each. The service goroutines read requests and

// then call srv.Handler to reply to them.

//

// For HTTP/2 support, srv.TLSConfig should be initialized to the

// provided listener's TLS Config before calling Serve. If

// srv.TLSConfig is non-nil and doesn't include the string "h2" in

// Config.NextProtos, HTTP/2 support is not enabled.

//

// Serve always returns a non-nil error. After Shutdown or Close, the

// returned error is ErrServerClosed.

func (srv *Server) Serve(l net.Listener) error {

    defer l.Close()

    if fn := testHookServerServe; fn != nil {

        fn(srv, l)

    }

    var tempDelay time.Duration // how long to sleep on accept failure

    if err := srv.setupHTTP2_Serve(); err != nil {

        return err

    }

    srv.trackListener(l, true)

    defer srv.trackListener(l, false)

    baseCtx := context.Background() // base is always background, per Issue 16220

    ctx := context.WithValue(baseCtx, ServerContextKey, srv)

    for {

        rw, e := l.Accept()

        if e != nil {

            select {

            case <-srv.getDoneChan():

                return ErrServerClosed

            default:

            }

            if ne, ok := e.(net.Error); ok && ne.Temporary() {

                if tempDelay ==  {

                    tempDelay =  * time.Millisecond

                } else {

                    tempDelay *=

                }

                if max :=  * time.Second; tempDelay > max {

                    tempDelay = max

                }

                srv.logf("http: Accept error: %v; retrying in %v", e, tempDelay)

                time.Sleep(tempDelay)

                continue

            }

            return e

        }

        tempDelay =

        c := srv.newConn(rw)

        c.setState(c.rwc, StateNew) // before Serve can return

        go c.serve(ctx)

    }

}

监听开启之后，一旦客户端请求到底，go就开启一个协程处理请求，主要逻辑都在serve方法之中。

serve方法比较长，其主要职能就是，创建一个上下文对象，然后调用Listener的Accept方法用来　获取连接数据并使用newConn方法创建连接对象。最后使用goroutine协程的方式处理连接请求。因为每一个连接都开起了一个协程，请求的上下文都不同，同时又保证了go的高并发。serve也是一个长长的方法：

// Serve a new connection.

func (c *conn) serve(ctx context.Context) {

    c.remoteAddr = c.rwc.RemoteAddr().String()

    ctx = context.WithValue(ctx, LocalAddrContextKey, c.rwc.LocalAddr())

    defer func() {

        if err := recover(); err != nil && err != ErrAbortHandler {

            const size =  <<

            buf := make([]byte, size)

            buf = buf[:runtime.Stack(buf, false)]

            c.server.logf("http: panic serving %v: %v\n%s", c.remoteAddr, err, buf)

        }

        if !c.hijacked() {

            c.close()

            c.setState(c.rwc, StateClosed)

        }

    }()

    if tlsConn, ok := c.rwc.(*tls.Conn); ok {

        if d := c.server.ReadTimeout; d !=  {

            c.rwc.SetReadDeadline(time.Now().Add(d))

        }

        if d := c.server.WriteTimeout; d !=  {

            c.rwc.SetWriteDeadline(time.Now().Add(d))

        }

        if err := tlsConn.Handshake(); err != nil {

            c.server.logf("http: TLS handshake error from %s: %v", c.rwc.RemoteAddr(), err)

            return

        }

        c.tlsState = new(tls.ConnectionState)

        *c.tlsState = tlsConn.ConnectionState()

        if proto := c.tlsState.NegotiatedProtocol; validNPN(proto) {

            if fn := c.server.TLSNextProto[proto]; fn != nil {

                h := initNPNRequest{tlsConn, serverHandler{c.server}}

                fn(c.server, tlsConn, h)

            }

            return

        }

    }

    // HTTP/1.x from here on.

    ctx, cancelCtx := context.WithCancel(ctx)

    c.cancelCtx = cancelCtx

    defer cancelCtx()

    c.r = &connReader{conn: c}

    c.bufr = newBufioReader(c.r)

    c.bufw = newBufioWriterSize(checkConnErrorWriter{c}, <<)

    for {

        w, err := c.readRequest(ctx)

        if c.r.remain != c.server.initialReadLimitSize() {

            // If we read any bytes off the wire, we're active.

            c.setState(c.rwc, StateActive)

        }

        if err != nil {

            const errorHeaders = "\r\nContent-Type: text/plain; charset=utf-8\r\nConnection: close\r\n\r\n"

            if err == errTooLarge {

                // Their HTTP client may or may not be

                // able to read this if we're

                // responding to them and hanging up

                // while they're still writing their

                // request. Undefined behavior.

                const publicErr = "431 Request Header Fields Too Large"

                fmt.Fprintf(c.rwc, "HTTP/1.1 "+publicErr+errorHeaders+publicErr)

                c.closeWriteAndWait()

                return

            }

            if isCommonNetReadError(err) {

                return // don't reply

            }

            publicErr := "400 Bad Request"

            if v, ok := err.(badRequestError); ok {

                publicErr = publicErr + ": " + string(v)

            }

            fmt.Fprintf(c.rwc, "HTTP/1.1 "+publicErr+errorHeaders+publicErr)

            return

        }

        // Expect 100 Continue support

        req := w.req

        if req.expectsContinue() {

            if req.ProtoAtLeast(, ) && req.ContentLength !=  {

                // Wrap the Body reader with one that replies on the connection

                req.Body = &expectContinueReader{readCloser: req.Body, resp: w}

            }

        } else if req.Header.get("Expect") != "" {

            w.sendExpectationFailed()

            return

        }

        c.curReq.Store(w)

        if requestBodyRemains(req.Body) {

            registerOnHitEOF(req.Body, w.conn.r.startBackgroundRead)

        } else {

            if w.conn.bufr.Buffered() >  {

                w.conn.r.closeNotifyFromPipelinedRequest()

            }

            w.conn.r.startBackgroundRead()

        }

        // HTTP cannot have multiple simultaneous active requests.[*]

        // Until the server replies to this request, it can't read another,

        // so we might as well run the handler in this goroutine.

        // [*] Not strictly true: HTTP pipelining. We could let them all process

        // in parallel even if their responses need to be serialized.

        // But we're not going to implement HTTP pipelining because it

        // was never deployed in the wild and the answer is HTTP/2.

        serverHandler{c.server}.ServeHTTP(w, w.req)

        w.cancelCtx()

        if c.hijacked() {

            return

        }

        w.finishRequest()

        if !w.shouldReuseConnection() {

            if w.requestBodyLimitHit || w.closedRequestBodyEarly() {

                c.closeWriteAndWait()

            }

            return

        }

        c.setState(c.rwc, StateIdle)

        c.curReq.Store((*response)(nil))

        if !w.conn.server.doKeepAlives() {

            // We're in shutdown mode. We might've replied

            // to the user without "Connection: close" and

            // they might think they can send another

            // request, but such is life with HTTP/1.1.

            return

        }

        if d := c.server.idleTimeout(); d !=  {

            c.rwc.SetReadDeadline(time.Now().Add(d))

            if _, err := c.bufr.Peek(); err != nil {

                return

            }

        }

        c.rwc.SetReadDeadline(time.Time{})

    }

}

serve方法

使用defer定义了函数退出时，连接关闭相关的处理。然后就是读取连接的网络数据，并处理读取完毕时候的状态。接下来就是调用serverHandler{c.server}.ServeHTTP(w, w.req)方法处理请求了。最后就是请求处理完毕的逻辑。serverHandler是一个重要的结构，它近有一个字段，即Server结构，同时它也实现了Handler接口方法ServeHTTP，并在该接口方法中做了一个重要的事情，初始化multiplexer路由多路复用器。如果server对象没有指定Handler，则使用默认的DefaultServeMux作为路由Multiplexer。并调用初始化Handler的ServeHTTP方法。

// serverHandler delegates to either the server's Handler or

// DefaultServeMux and also handles "OPTIONS *" requests.

type serverHandler struct {

    srv *Server

}

func (sh serverHandler) ServeHTTP(rw ResponseWriter, req *Request) {

    handler := sh.srv.Handler

    if handler == nil {

        handler = DefaultServeMux

    }

    if req.RequestURI == "*" && req.Method == "OPTIONS" {

        handler = globalOptionsHandler{}

    }

    handler.ServeHTTP(rw, req)

}

这里DefaultServeMux的ServeHTTP方法其实也是定义在ServeMux结构中的，相关代码如下：

// Find a handler on a handler map given a path string.

// Most-specific (longest) pattern wins.

func (mux *ServeMux) match(path string) (h Handler, pattern string) {

    // Check for exact match first.

    v, ok := mux.m[path]

    if ok {

        return v.h, v.pattern

    }

    // Check for longest valid match.

    var n =

    for k, v := range mux.m {

        if !pathMatch(k, path) {

            continue

        }

        if h == nil || len(k) > n {

            n = len(k)

            h = v.h

            pattern = v.pattern

        }

    }

    return

}

func (mux *ServeMux) Handler(r *Request) (h Handler, pattern string) {

    // CONNECT requests are not canonicalized.

    if r.Method == "CONNECT" {

        return mux.handler(r.Host, r.URL.Path)

    }

    // All other requests have any port stripped and path cleaned

    // before passing to mux.handler.

    host := stripHostPort(r.Host)

    path := cleanPath(r.URL.Path)

    if path != r.URL.Path {

        _, pattern = mux.handler(host, path)

        url := *r.URL

        url.Path = path

        return RedirectHandler(url.String(), StatusMovedPermanently), pattern

    }

    return mux.handler(host, r.URL.Path)

}

// handler is the main implementation of Handler.

// The path is known to be in canonical form, except for CONNECT methods.

func (mux *ServeMux) handler(host, path string) (h Handler, pattern string) {

    mux.mu.RLock()

    defer mux.mu.RUnlock()

    // Host-specific pattern takes precedence over generic ones

    if mux.hosts {

        h, pattern = mux.match(host + path)

    }

    if h == nil {

        h, pattern = mux.match(path)

    }

    if h == nil {

        h, pattern = NotFoundHandler(), ""

    }

    return

}

// ServeHTTP dispatches the request to the handler whose

// pattern most closely matches the request URL.

func (mux *ServeMux) ServeHTTP(w ResponseWriter, r *Request) {

    if r.RequestURI == "*" {

        if r.ProtoAtLeast(, ) {

            w.Header().Set("Connection", "close")

        }

        w.WriteHeader(StatusBadRequest)

        return

    }

    h, _ := mux.Handler(r)

    h.ServeHTTP(w, r)

}

mux的ServeHTTP方法通过调用其Handler方法寻找注册到路由上的handler函数，并调用该函数的ServeHTTP方法，本例则是IndexHandler函数。 mux的Handler方法对URL简单的处理，然后调用handler方法，后者会创建一个锁，同时调用match方法返回一个handler和pattern。在match方法中，mux的m字段是map[string]muxEntry图，后者存储了pattern和handler处理器函数，因此通过迭代m寻找出注册路由的patten模式与实际url匹配的handler函数并返回。返回的结构一直传递到mux的ServeHTTP方法，接下来调用handler函数的ServeHTTP方法，即IndexHandler函数，然后把response写到http.RequestWirter对象返回给客户端。上述函数运行结束即`serverHandler{c.server}.ServeHTTP(w, w.req)`运行结束。接下来就是对请求处理完毕之后上希望和连接断开的相关逻辑。至此，Golang中一个完整的http服务介绍完毕，包括注册路由，开启监听，处理连接，路由处理函数。

总结

多数的web应用基于HTTP协议，客户端和服务器通过request-response的方式交互。一个server并不可少的两部分莫过于路由注册和连接处理。Golang通过一个ServeMux实现了的multiplexer路由多路复用器来管理路由。同时提供一个Handler接口提供ServeHTTP用来实现handler处理其函数，后者可以处理实际request并构造response。 ServeMux和handler处理器函数的连接桥梁就是Handler接口。ServeMux的ServeHTTP方法实现了寻找注册路由的handler的函数，并调用该handler的ServeHTTP方法。ServeHTTP方法就是真正处理请求和构造响应的地方。回顾go的http包实现http服务的流程，可见大师们的编码设计之功力。学习有利提高自身的代码逻辑组织能力。更好的学习方式除了阅读，就是实践，接下来，我们将着重讨论来构建http服务。尤其是构建http中间件函数。

四、HTTP客户端工具

net/http不仅提供了服务端处理，还提供了客户端处理功能。

http包中提供了Get、Post、Head、PostForm方法实现HTTP请求：

//GET

func Get(url string) (resp *Response, err error) {

    return DefaultClient.Get(url)

}

//POST

func Post(url string, contentType string, body io.Reader) (resp *Response, err error) {

    return DefaultClient.Post(url, contentType, body)

}

//HEAD

func Head(url string) (resp *Response, err error) {

    return DefaultClient.Head(url)

}

//POSTFORM

func PostForm(url string, data url.Values) (resp *Response, err error) {

    return DefaultClient.PostForm(url, data)

}

GET请求示例

package main

import (

    "fmt"

    "net/http"

    "log"

    "reflect"

    "bytes"

)

func main() {

    resp, err := http.Get("http://www.baidu.com")

    if err != nil {

        // 错误处理

        log.Println(err)

        return

    }

    defer resp.Body.Close() //关闭链接

    headers := resp.Header

    for k, v := range headers {

        fmt.Printf("k=%v, v=%v\n", k, v) //所有头信息

    }

    fmt.Printf("resp status %s,statusCode %d\n", resp.Status, resp.StatusCode)

    fmt.Printf("resp Proto %s\n", resp.Proto)

    fmt.Printf("resp content length %d\n", resp.ContentLength)

    fmt.Printf("resp transfer encoding %v\n", resp.TransferEncoding)

    fmt.Printf("resp Uncompressed %t\n", resp.Uncompressed)

    fmt.Println(reflect.TypeOf(resp.Body))

    buf := bytes.NewBuffer(make([]byte, , ))

    length, _ := buf.ReadFrom(resp.Body)

    fmt.Println(len(buf.Bytes()))

    fmt.Println(length)

    fmt.Println(string(buf.Bytes()))

}

使用http.Do设置请求头、cookie等

package main

import (

    "net/http"

    "strings"

    "io/ioutil"

    "log"

    "fmt"

)

func main() {

    client := &http.Client{}

    req, err := http.NewRequest("POST", "http://www.baidu.com",

        strings.NewReader("name=xxxx&passwd=xxxx"))

    if err != nil {

        fmt.Println(err)

        return

    }

    req.Header.Set("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8") //设置请求头信息

    resp, err := client.Do(req)

    defer resp.Body.Close()

    body, err := ioutil.ReadAll(resp.Body)

    if err != nil {

        log.Println(err)

        return

    }

    var res string

    res = string(body[:])

    fmt.Println(res)

}

POST请求示例

package main

import (

    "net/http"

    "strings"

    "fmt"

    "io/ioutil"

)

func main() {

    resp, err := http.Post("http://www.baidu.com",

        "application/x-www-form-urlencoded",

        strings.NewReader("username=xxx&password=xxxx"))

    if err != nil {

        fmt.Println(err)

        return

    }

    defer resp.Body.Close()

    body, err := ioutil.ReadAll(resp.Body)

    if err != nil {

        fmt.Println(err)

        return

    }

    fmt.Println(string(body))

}

PostForm请求示例

package main

import (

    "net/http"

    "fmt"

    "io/ioutil"

    "net/url"

)

func main() {

    postParam := url.Values{

        "name":      {"wd"},

        "password": {""},

    }

    resp, err := http.PostForm("https://cn.bing.com/", postParam)

    if err != nil {

        fmt.Println(err)

        return

    }

    defer resp.Body.Close()

    body, err := ioutil.ReadAll(resp.Body)

    if err != nil {

        fmt.Println(err)

        return

    }

    fmt.Println(string(body))

}