0. 简述

Go是一个开源的编程语言，它能让构造简单、可靠且高效的软件变得容易。

Go语言被设计成一门应用于搭建web服务器，存储集群或类似用途的巨型中央服务器的系统编程语言。对于高性能分布式系统领域而言，Go语言无疑比大多数其他语言有着更高的开发效率。它提供了海量并行的支持，这对于游戏服务器端的开发而言是再好不过的。

Go官网：https: ​


package main import "fmt" func main() {     fmt.Println("Hello, World!") }


X86上编译运行：


wang@ubuntu:~/go$ go build -o hello hello.go wang@ubuntu:~/go$ ./hello Hello, World!


或直接运行


wang@ubuntu:~/go$ go run hello.go Hello, World!


X86平台交叉编译ARM64平台上程序：


GOOS=linux GOARCH=arm64 go build -o hello hello.go wang@ubuntu:~/go$ file hello hello: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), statically linked, not stripped


godoc用法：


godoc -http=localhost:6060 -play


godoc可提供离线的go文档，便于本地查看。

可 搜索所有golang库的接口说明。

1. Go编译器

两种官方编译器，gc和gccgo，其中gccgo基于gcc后端。

go编译器支持8种指令集，不同建构编译质量不同：


amd64 (also known as x86-64)     386 (x86 or x86-32)   Comparable to the amd64 port. arm (ARM) Supports Linux, FreeBSD, NetBSD, OpenBSD and Darwin binaries. Less widely used than the other ports. arm64 (AArch64) Supports Linux and Darwin binaries. New in 1.5 and not as well exercised as other ports. ppc64, ppc64le (64-bit PowerPC big- and little-endian) Supports Linux binaries. New in 1.5 and not as well exercised as other ports. mips, mipsle (32-bit MIPS big- and little-endian) Supports Linux binaries. New in 1.8 and not as well exercised as other ports. mips64, mips64le (64-bit MIPS big- and little-endian) Supports Linux binaries. New in 1.6 and not as well exercised as other ports. s390x (IBM System z) Supports Linux binaries. New in 1.7 and not as well exercised as other ports.


go编译环境可以被定制，与平台和建构相关的是$GOOS和$GOARCH，分别指定目标操作系统和目标建构。常用组合如下：（注：$GOOS是darwin for macOS 10.1及以上和iOS）


$GOOS        $GOARCH android     arm darwin      386 darwin      amd64 darwin      arm darwin      arm64 linux       386 linux       amd64 linux       arm linux       arm64 windows     386 windows     amd64


go编译器（或go环境）安装

有两种安装方式：二进制发布包和源码包，参考https://golang.google.cn/doc/install。一般情况下可直接下载二进制发布包，官方已提供了常用平台的二进制发布包。

下载二进制tar包，tar -C /usr/local -xzf go$VERSION.$OS-$ARCH.tar.gz，一般安装路径为/usr/local，go工具命令要执行需要将/usr/local/go/bin导出到PATH环境变量中（/etc/profile可长期有效）。

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ubuntu下可直接apt安装：


sudo apt-get install golang-go


go工具卸载

linux下直接删除/usr/local/go目录即可（同时修改PATH环境变量，或/etc/profile）。

GO环境变量

go env可打印go环境变量。

$GOPATH

GOPATH指定workspace位置，默认为$home/go，go项目在本地的开发环境的项目根路径（以便项目编译，go build, go install，go get）。若工作在其他目录，需设定GOPATH。export GOPATH=$HOME/go

或直接写到/etc/profile中，然后source /etc/profile

注意GOPATH不能和go安装目录相同。


go env GOPATH


打印当前有效的GOPATH，若没有设置打印默认位置。

For convenience, add the workspace's bin subdirectory to your PATH:


$ export PATH=$PATH:$(go env GOPATH)/bin


GOPATH之下主要包含三个目录：bin，pkg，src。bin目录主要存放可执行文件；pkg目录存放编译好的库文件，主要是*.a文件；src目录下主要存放go的源文件。

$GOROOT

go的安装目录，配置后不会更改。一般为/usr/local/go或/usr/go或/usr/lib/go。

$GOROOT_FINAL

$GOOS and $GOARCH

用于不同平台的交叉编译，只需要在build之前设置这两个变量即可，这也是go语言的优势之一：可以编译生成跨平台运行的可执行文件。

注意：这个交叉编译暂不支持cgo方式，因此交叉编译时需要设置$CGO_ENABLED设置为0。

$GOHOSTOS and $GOHOSTARCH

$GOBIN

go二进制文件安装目录，默认为$GOROOT/bin。

$GO386

$GOARM

$GOMIPS

集成开发环境IDE

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2. cgo

Cgo lets Go packages call C code.

The basics

If a Go source file imports ​​"C"​​​, it is using cgo. The Go file will have access to anything appearing in the comment immediately preceding the line ​​import "C"​​, and will be linked against all other cgo comments in other Go files, and all C files included in the build process.

Note that there must be no blank lines in between the cgo comment and the import statement.

To access a symbol originating from the C side, use the package name ​​C​​​. That is, if you want to call the C function ​​printf()​​​ from Go code, you write ​​C.printf()​​​. Since variable argument methods like printf aren't supported yet (issue ​​975​​), we will wrap it in the C method "myprint":


package main  /* #include <stdio.h> #include <stdlib.h>  void myprint(char* s) {     printf("%s", s); } */ import "C"  import "unsafe"  func main() {     cs := C.CString("Hello from stdio\n")     C.myprint(cs)     C.free(unsafe.Pointer(cs)) }


 

3. Go交叉编译

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If cgo is not required (common go programs, not including c/c++)

The go tool won’t require any bootstrapping if cgo is not required. That allows you to target the following program to any GOOS/GOARCH without requiring you to do any additional work. Invoke go build.


$ cat main.go package main import "fmt" func main() {     fmt.Println("hello world") }


In order to target android/arm, run the following command.


$ GOOS=android GOARCH=arm GOARM=7 go build .


The produced binary is targeting ARMv7 processors that runs Android. All possible GOOS and GOARCH values are liste 

If cgo is required (including c/c++)

If you need to have cgo enabled, the go tool allows you to provide custom C and C++ compilers via CC and CXX environment variables.


$ CGO_ENABLED=1 CC=android-armeabi-gcc CXX=android-armeabi-g++ \     GOOS=android GOARCH=arm GOARM=7 go build .


The toolchain will invoke android-armeabi-gcc and android-armeabi-g++ if it is required to compile any part of the package with a C or C++ compiler. Consider the following program with a slightly different main function. Rather than outputting “hello world” to the standard I/O, it will use Android system libraries to write “hello world” to the system log.


$ cat main.go // +build android  package main  // #cgo LDFLAGS: -llog // // #include <android/log.h> // // void hello() { //   __android_log_print( //     ANDROID_LOG_INFO, "MyProgram", "hello world"); // } import "C" func main() {     C.hello() }


If you build the program with the command above and examine the build with -x, you can observe that cgo is delegating the C compilation to arm-linux-androideabi-gcc.


$ CGO_ENABLED=1 \ CC=arm-linux-androideabi-gcc \ CXX=arm-linux-androideabi-g++ \ GOOS=android GOARCH=arm GOARM=7 go build -x . ... CGO_LDFLAGS=”-g” “-O2” “-llog” /Users/jbd/go/pkg/tool/darwin_amd64/cgo -objdir $WORK/github.com/rakyll/hello/_obj/ -importpath github.com/rakyll/hello — -I $WORK/github.com/rakyll/hello/_obj/ main.go arm-linux-androideabi-gcc -I . -fPIC -marm -pthread -fmessage-length=0 -print-libgcc-file-name arm-linux-androideabi-gcc -I . -fPIC -marm -pthread -fmessage-length=0 -I $WORK/github.com/rakyll/hello/_obj/ -g -O2 -o $WORK/github.com/rakyll/hello/_obj/_cgo_main.o -c $WORK/github.com/rakyll/hello/_obj/_cgo_main.c ...


Pre-building the standard library

The go tool also provides a utility if you would like to pre-build the standard library, targeting a specific GOOS and GOARCH.


$ CGO_ENABLED=1 \     CC=arm-linux-androideabi-gcc \     CXX=arm-linux-androideabi-g++ \     GOOS=android GOARCH=arm GOARM=7 go install std


The standard library targeting android/armv7 will be available at $GOROOT/pkg/android_arm.


$ ls $GOROOT/pkg/android_arm archive    fmt.a      math       runtime.a bufio.a    go         math.a     sort.a bytes.a    hash       mime       strconv.a compress   hash.a     mime.a     strings.a container  html       net        sync crypto     html.a     net.a      sync.a crypto.a   image      os         syscall.a database   image.a    os.a       testing debug      index      path       testing.a encoding   internal   path.a     text encoding.a io         reflect.a  time.a errors.a   io.a       regexp     unicode expvar.a   log        regexp.a   unicode.a flag.a     log.a      runtime


If you prefer not to pre-build and install the standard library to the GOROOT, required libraries will be built while building user packages. But, the standard libraries builds are not preserved for future use at this stage and they will be rebuilt each time you run go build.

4. golang代理

由于网络限制，一般要使用代理获取仓库。

golang代理使用proxy.cn， ​

使用方法：

$ export GOPROXY=https://goproxy.cn

或

$ export GO111MODULE=on

$ export GOPROXY=https://goproxy.cn

或直接写入：～/.bash_profile

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