go 工程搭建

go 路径问题: go install 下载到$GOPATH/bin 下生成exe，$GOPATH/bkg下载包

cd 到目标文件目录，go install，

cd $GOPATH/bin

./main.exe

go get 对比 go install: https://juejin.cn/post/7223241078942613564

Key Differences

Feature	`go get`	`go install`
Purpose	Fetches and installs packages and dependencies	Compiles and installs a Go package as a binary
Modifies go.mod	Yes, updates dependencies	No, does not modify go.mod
Usage	Adding or updating dependencies	Installing binaries
Output	Downloads source code and updates module files	Builds and installs binary in `$GOPATH/bin` or `$GOBIN`
Typical Use	Managing dependencies	Installing Go command-line tools

go get: Use this command for managing your project's dependencies, adding new packages, and updating existing ones. It modifies the go.mod file to reflect these changes.
go install: Use this command to compile and install Go packages as binaries, especially useful for installing command-line tools. It does not affect your project's dependency files.

goland 执行main.go，编译到哪里？如何执行？

C:/Users/Administrator/appData/Local/Temp 生成临时编译文件

go install & go build 区别：https://juejin.cn/post/6844903938060222471

go 编译成linux形式：

go env -w CGO_ENABLED=0 GOOS=linux GOARCH=amd64 
go build main.go

Go build

#Mac下编译Linux, Windows平台的64位可执行程序：
$ go env -w CGO_ENABLED=0 GOOS=linux GOARCH=amd64
$ go env -w CGO_ENABLED=0 GOOS=windows GOARCH=amd64

#Linux下编译Mac, Windows平台的64位可执行程序：
$ go env -w CGO_ENABLED=0 GOOS=darwin GOARCH=amd64 
$ go env -w CGO_ENABLED=0 GOOS=windows GOARCH=amd64 

#Windows下编译Mac, Linux平台的64位可执行程序：
$ go env -w CGO_ENABLED=0 GOOS=darwin3 GOARCH=amd64 
$ go env -w CGO_ENABLED=0 GOOS=linux GOARCH=amd64 

#执行编译
go build -o "你要存储编译后的文件到哪里？" main.go

manage dependencies

//package 组织源码，go源码的集合，复用代码
// same directory same package
//一般是目录名和包保持一致

import (
"fmt"
n "learngo/ch1/user"
_ "learngo/ch2/user" // use to init() to print log
)

//install

1. IDE sync the package
2. cd 到目录
go get github/.../v8
go get -u (update to the latest)
go get github/.../v8@version // version

go mod help
go mod graph // dependencies
go mod tidy // clean and organize

go install
error=> unresolved reference: File->invalidate caches

go edit -replace

go edit -replace github/.../A=github/.../project-A@v1.0.0

regulation

1. naming
package:
1.same as directory
2.meaningful
3.lowercase

file:
1.user_name.go // lowercase

variable:
1. userName
2. UserName
3. un
4. URLVersion
5. (bool) has is can

struct:User
interface:
-er: Writer
IRead
const: APP_VERSION // UPPERCASE

2. comment // /**/

note the sequence of importing

import(
"os" // system

"gorm.io/gorm" // third-party

"src.imooc/bobby/A" inner
)

unit test

go test: in the package, run all files ended with _test.go
Test has 4 categories:
1) Test_ for functionality
2) Benchmark for performance
3) example
4) ambiguous test

1> demo

package ch11

import "testing"

func Test_add(t *testing.T) {
    res := add(1, 3)
    if res != 4 {
        t.Errorf("expect %d, actual get %d", 4, res)
    }
}

also can cd to the ch11 and run "go test"

2> how to skip time-consuming test

purpose: skip Test_add2()

func Test_add2(t *testing.T) {
    fmt.Println("111111")
    if testing.Short() {
        fmt.Println("22222")
        t.Skip("skippppppp")
    } // this is the end
   .... // not reach the code here

3> Table driven test unit: 当我不想调用gorm去连接数据库，想直接测试。可以提前把数据录入进表格。（设置期望）

func Test_add3(t *testing.T) {
    var u = []struct {
        a   int
        b   int
        out int
    }{
        {1, 1, 2},
        {1, 1, 2},
        {2, 2, 4},
    }
    for _, value := range u {
        re := add(value.a, value.b)
        if re != value.out {
            t.Errorf("expect %d, actual get %d", value.out, re)
        }
    }
}

Benchmark

purpose: compare the performance of 3 kinds of way to construct string

const numbers = 10000
func BenchmarkSprintf(bb *testing.B) {
    bb.ResetTimer()
    for i := 0; i < bb.N; i++ {
        var str string
        for j := 0; j < numbers; j++ {
            str = fmt.Sprintf("%s%d", str, j)
        }
    }
    bb.StopTimer()
}
func BenchmarkStringBuilder(bb *testing.B) {
    bb.ResetTimer()
    for i := 0; i < bb.N; i++ {
        var builder strings.Builder
        for j := 0; j < numbers; j++ {
            builder.WriteString(strconv.Itoa(j))
        }
        _ = builder.String()
    }
    bb.StopTimer()
}
func BenchmarkStringAdd(bb *testing.B) {
    bb.ResetTimer()
    for i := 0; i < bb.N; i++ {
        var str string
        for j := 0; j < numbers; j++ {
            str = str + strconv.Itoa(j)
        }
    }
    bb.StopTimer()
}