go语言简述
0. 簡(jiǎn)述
Go是一個(gè)開(kāi)源的編程語(yǔ)言，它能讓構(gòu)造簡(jiǎn)單、可靠且高效的軟件變得容易。
Go語(yǔ)言被設(shè)計(jì)成一門(mén)應(yīng)用于搭建web服務(wù)器，存儲(chǔ)集群或類(lèi)似用途的巨型中央服務(wù)器的系統(tǒng)編程語(yǔ)言。對(duì)于高性能分布式系統(tǒng)領(lǐng)域而言，Go語(yǔ)言無(wú)疑比大多數(shù)其他語(yǔ)言有著更高的開(kāi)發(fā)效率。它提供了海量并行的支持，這對(duì)于游戲服務(wù)器端的開(kāi)發(fā)而言是再好不過(guò)的。
Go官網(wǎng)：https://golang.google.cn/或https://github.com/golang/go
package main
import "fmt"
func main() {
fmt.Println("Hello, World!")
}
X86上編譯運(yùn)行：
wang@ubuntu:~/go$ go build -o hello hello.go wang@ubuntu:~/go$ ./hello Hello, World!
或直接運(yùn)行
wang@ubuntu:~/go$ go run hello.go Hello, World!
X86平臺(tái)交叉編譯ARM64平臺(tái)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可提供離線(xiàn)的go文檔，便于本地查看。
可在https://godoc.org/中搜索所有g(shù)olang庫(kù)的接口說(shuō)明。
1. Go編譯器
兩種官方編譯器，gc和gccgo，其中g(shù)ccgo基于gcc后端。
go編譯器支持8種指令集，不同建構(gòu)編譯質(zhì)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編譯環(huán)境可以被定制，與平臺(tái)和建構(gòu)相關(guān)的是$GOOS和$GOARCH，分別指定目標(biāo)操作系統(tǒng)和目標(biāo)建構(gòu)。常用組合如下：（注：$GOOS是darwin for macOS 10.1及以上和iOS）
$GOOS $GOARCH android arm darwin 386 darwin amd64 darwin arm darwin arm64 linux 386 linux amd64 linux arm linux arm64 windows 386 windows amd64
go編譯器（或go環(huán)境）安裝
有兩種安裝方式：二進(jìn)制發(fā)布包和源碼包，參考https://golang.google.cn/doc/install。一般情況下可直接下載二進(jìn)制發(fā)布包，官方已提供了常用平臺(tái)的二進(jìn)制發(fā)布包。
下載二進(jìn)制tar包，tar -C /usr/local -xzf go$VERSION.$OS-$ARCH.tar.gz，一般安裝路徑為/usr/local，go工具命令要執(zhí)行需要將/usr/local/go/bin導(dǎo)出到PATH環(huán)境變量中（/etc/profile可長(zhǎng)期有效）。
源碼包安裝方式參考：Installing Go from source
ubuntu下可直接apt安裝：
sudo apt-get install golang-go
go工具卸載
linux下直接刪除/usr/local/go目錄即可（同時(shí)修改PATH環(huán)境變量，或/etc/profile）。
GO環(huán)境變量
go env可打印go環(huán)境變量。
$GOPATH
GOPATH指定workspace位置，默認(rèn)為$home/go，go項(xiàng)目在本地的開(kāi)發(fā)環(huán)境的項(xiàng)目根路徑（以便項(xiàng)目編譯，go build, go install，go get）。若工作在其他目錄，需設(shè)定GOPATH。export GOPATH=$HOME/go
或直接寫(xiě)到/etc/profile中，然后source /etc/profile
注意GOPATH不能和go安裝目錄相同。
go env GOPATH
打印當(dāng)前有效的GOPATH，若沒(méi)有設(shè)置打印默認(rèn)位置。
For convenience, add the workspace'sbinsubdirectory to yourPATH:
$ export PATH=$PATH:$(go env GOPATH)/bin
GOPATH之下主要包含三個(gè)目錄：bin，pkg，src。bin目錄主要存放可執(zhí)行文件；pkg目錄存放編譯好的庫(kù)文件，主要是*.a文件；src目錄下主要存放go的源文件。
$GOROOT
go的安裝目錄，配置后不會(huì)更改。一般為/usr/local/go或/usr/go或/usr/lib/go。
$GOROOT_FINAL
$GOOS and $GOARCH
用于不同平臺(tái)的交叉編譯，只需要在build之前設(shè)置這兩個(gè)變量即可，這也是go語(yǔ)言的優(yōu)勢(shì)之一：可以編譯生成跨平臺(tái)運(yùn)行的可執(zhí)行文件。
注意：這個(gè)交叉編譯暫不支持cgo方式，因此交叉編譯時(shí)需要設(shè)置$CGO_ENABLED設(shè)置為0。
$GOHOSTOS and $GOHOSTARCH
$GOBIN
go二進(jìn)制文件安裝目錄，默認(rèn)為$GOROOT/bin。
$GO386
$GOARM
$GOMIPS
集成開(kāi)發(fā)環(huán)境IDE
vscode-golang配置參考：VS code golang 開(kāi)發(fā)環(huán)境搭建
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 lineimport "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 nameC. That is, if you want to call the C functionprintf()from Go code, you writeC.printf(). Since variable argument methods like printf aren't supported yet (issue975), 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
")
C.myprint(cs)
C.free(unsafe.Pointer(cs))
}
參考：
1. http://golang.org/doc/articles/c_go_cgo.html
2.https://github.com/golang/go/wiki/cgo
3.http://wiki.jikexueyuan.com/project/go-command-tutorial/0.13.html 極客學(xué)院go命令詳解
4. https://books.studygolang.com/advanced-go-programming-book/ch2-cgo/readme.htmlGo語(yǔ)言高級(jí)編程（Advanced Go Programming）cgo編程
3. Go交叉編譯
參考：Go cross compilation
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. Invokego 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 listed on theenvironment docs.
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 rungo build.
go語(yǔ)言學(xué)習(xí)參考：
1.Go 系列教程（Golang tutorial series） go語(yǔ)言中文網(wǎng)
2. go入門(mén)指南博客
3. go語(yǔ)言學(xué)習(xí)博客
4.go基礎(chǔ)學(xué)習(xí) coder python修行路
5.beego項(xiàng)目https://beego.me
6.https://github.com/golang/go
7．How to write Go Codehttps://golang.google.cn/doc/code.html
8．https://golang.google.cn/提供go在線(xiàn)測(cè)試環(huán)境和文檔
9．https://golang.google.cn/doc/go相關(guān)文檔
10．https://golang.google.cn/pkg/go標(biāo)準(zhǔn)庫(kù)
11.https://godoc.org/ go實(shí)用庫(kù)搜索
12.https://books.studygolang.com/advanced-go-programming-book/ch2-cgo/readme.htmlGo語(yǔ)言高級(jí)編程（Advanced Go Programming）
13.在 GitHub 上構(gòu)建一個(gè)看上去正規(guī)的 Golang 項(xiàng)目
14.Go 語(yǔ)言設(shè)計(jì)與實(shí)現(xiàn)
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