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# What’s New in Go 1.21 a Comprehensive Notes
# Go 1.21 中新增功能的全面概述

- 原文地址：https://younisjad.medium.com/whats-new-in-go-1-21-a-comprehensive-notes-96017750b390
- 原文作者：Younis Jad
- 本文永久链接：
- 本文永久链接：https://github.com/gocn/translator/blob/master/2023/w26_Whats_New_in_Go_1.21_a_Comprehensive_Notes.md
- 译者：[lsj1342](https://github.com/lsj1342)
- 校对：[]()
- 校对：[zxmfke](https://github.com/zxmfke)
***

![Go 1.21 Exciting Updates and Enhancements: A Comprehensive Overview](https://github.com/gocn/translator/raw/master/static/images/2023/w26/1*OWUGPbMTINTQEZmSi3n-hQ.png)
![Go 1.21 Exciting Updates and Enhancements: A Comprehensive Overview](https://github.com/gocn/translator/raw/master/static/images/2023/w26/1_OWUGPbMTINTQEZmSi3n-hQ.png)


The Go programming language has released its first Release Candidate (RC) for version 1.21, which is packed with new features, improvements, and performance enhancements. This article provides an overview of the notable changes and features in Go 1.21, along with some exciting additions to the standard library.
Go 语言发布了 1.21 版本的第一个候选版本 (RC)，其中包含新的功能、改进和性能提升。本文概述了 Go 1.21 中的显著变化和功能，以及标准库中的一些令人兴奋的新增内容。

## Tool Improvements:
## 工具改进：

## The Profile Guided Optimization (PGO) feature
## 配置文件引导优化 (PGO) 功能

In Go 1.21, the process of enabling PGO optimization has been streamlined. By default, the standard approach is to store a pprof CPU profile with the filename “default.pgo” in the main package directory of the profiled binary. This profile is automatically detected by the go build command, enabling PGO optimizations during the build.
在 Go 1.21 中，启用 PGO 优化的过程已得到简化。默认情况下，标准方法是将文件名“default.pgo”的 pprof CPU 配置文件存储在分析二进制文件的主包目录中。go build 命令会自动检测此配置文件，从而在构建过程中启用 PGO 优化。

```
# Store default.pgo profile in the main package directory
# 将 default.pgo 配置文件存储在主包目录中
$ go build
# Assuming default.pgo exists, PGO optimizations will be applied during the build process
# 如果存在 default.pgo，在构建过程中将会应用 PGO 优化
```

**Committing Profiles in Source Repository**
**在源代码仓库中提交配置文件**

To ensure reproducible and performant builds, it is recommended to commit the profiles directly into the source repository. This approach simplifies the build experience as there are no additional steps required to fetch the profiles other than fetching the source code.
为了确保可重复且高性能的构建，建议将配置文件直接提交到源代码仓库中。这种方法简化了构建方式，因为除了获取源代码之外，不需要任何额外的步骤来获取配置文件。

```
# Committing default.pgo profile in the source repository
# 提交 default.pgo 配置文件到源代码仓库中
├── main.go
└── default.pgo
# Developers can directly build the code with the committed profile
# 开发者可以直接使用提交的配置文件构建代码
$ go build
```

**Advanced PGO Profile Selection**
**PGO 配置文件的选择**

In more complex scenarios, the go build command provides the `-pgo` flag to control the PGO profile selection. By default, this flag is set to -`pgo=auto,` which follows the behavior described above using the `default.pgo` profile.
在更复杂的场景中，`go build` 命令也提供了 `-pgo` 标识来控制 PGO 配置文件的选择。此标志默认为 `-pgo=auto`，将会使用 `default.pgo` 文件。

```
# Using -pgo flag to manually specify the profile for optimization
# 使用 -pgo 标志手动指定配置文件
$ go build -pgo=/tmp/foo.pprof
```

**Disabling PGO Optimization**
**禁用 PGO 优化**

In cases where PGO optimizations are not desired, the `-pgo` flag can be set to `-pgo=off` to disable them entirely.
如果不需要 PGO 优化，可以将 `-pgo` 标志设置为 `-pgo=off` 来完全禁用它们。

```
# Disabling PGO optimizations using the -pgo flag
# 使用 -pgo 标志禁用 PGO 优化
$ go build -pgo=off
```

These examples demonstrate the usage of the go build command for simplicity. The same principles apply to other build commands such as go install and go run.
这些示例简单演示了 go build 命令的用法，相同的原则也适用于其他构建命令，例如 go install 和 go run。

> Note: Starting from Go 1.21, PGO optimizations are enabled by default. Prior to Go 1.21, PGO had to be explicitly enabled using the -pgo flag.
> 注意：从 Go 1.21 开始，默认启用 PGO 优化。在 Go 1.21 之前，必须使用 -pgo 标志显式启用 PGO。
## Backward and Forward Language Compatibility
## 向后和向前语言兼容性

Go 1.21 introduces backward and forward language compatibility support in the go tool, making it easier for developers to ensure their code remains compatible with different language versions.
Go 1.21 在 go 工具中引入了向后和向前的语言兼容性支持，使开发人员更容易确保他们的代码与不同语言版本保持兼容。

Example: Testing package with //go:debug directive in \*\_test.go file
示例：在 *_test.go 文件中使用 //go:debug 指令

```
package mypackage_test
Expand All @@ -77,50 +76,50 @@ import (
)
func TestMyFunction(t *testing.T)
{
// Test code
// 测试代码
result := mypackage.MyFunction()
// Assertion code
// 断言代码
}
```

In this example, the `//go:debug mysetting=1` directive is included in the `*_test.go` file of the package being tested. This directive serves as a directive for the test’s main package and can override the default behavior for specific debug settings during testing. This allows different test scenarios to be executed by enabling specific debug settings.
在此示例中，`//go:debug mysetting=1` 指令包含在测试包的 *_test.go 文件中。该指令用于测试 main 包，并且可以覆盖测试期间特定调试设置的默认行为。这允许通过启用特定的调试设置来执行不同的测试场景。

**Reporting default GODEBUG settings for a main package**
**列出 main 包的默认 GODEBUG 设置**

```
go list -f '{{.DefaultGODEBUG}}' my/main/package
```

When executing this command, where my/main/package is the path to the main package, the Go toolchain will report the default GODEBUG settings that will be compiled into the main package. This command is useful to see the differences from the base Go toolchain defaults.
执行此命令时，其中 my/main/package 是主包的路径，Go 工具链将列出会编译到主包的默认 GODEBUG 设置。此命令对于查看当前设置与基本 Go 工具链默认值的差异时非常有用。

## Language Changes:
## 语言变化：

## New Built-in Functions: min, max, and clear
## 新的内置函数：min、max 和 clear

Go 1.21 introduces three new built-in functions, namely min, max, and clear, which provide convenient options for performing basic operations on numeric data.
Go 1.21 引入了三个新的内置函数: min、max 和 clear，它们为对数值的操作提供了方便的选项。

**Min, Max Functions**
**最小、最大值函数**

The min and max functions are built-in functions in Go that calculate the smallest or largest value, respectively, among a fixed number of arguments of ordered types. These functions require at least one argument to be passed.
min 和 max 函数成为了 Go 中的内置函数，它们分别能够计算固定数量的有序类型数据的最小值或最大值。这些函数需要至少传递一个参数。

The same type rules that apply to operators also apply to these functions. For ordered arguments x and y, calling min(x, y) is valid if the addition x + y is valid. The type of the result returned by min(x, y) is the same as the type of x + y, and the same applies to the max function. If all the arguments passed to these functions are constant, the result returned by these functions is also constant.
适用于运算符规则的数据类型也同样适用于这些函数。对于有序参数 x 和 y，如果加法 x + y 有效，则调用 min(x, y) 也是有效的。min(x, y) 返回结果的类型与 x + y 的类型相同，对于 max 函数也是如此。如果传递给这些函数的所有参数都是常量，那么这些函数返回的结果也是常量。

```go
var x, y int
m := min(x) // m == x
m := min(x, y) // m is the smaller of x and y
m := max(x, y, 10) // m is the larger of x and y but at least 10
c := max(1, 2.0, 10) // c == 10.0 (floating-point kind)
f := max(0, float32(x)) // type of f is float32
m := min(x, y) // m 是 x 和 y 的最小值
m := max(x, y, 10) // m 是 x 和 y 中较大的一个，但至少为 10
c := max(1, 2.0, 10) // c == 10.0 (浮点型)
f := max(0, float32(x)) // f 为 float32 类型
var s []string
_ = min(s...) // invalid: slice arguments are not permitted
t := max("", "foo", "bar") // t == "foo" (string kind)
_ = min(s...) // 无效：不允许使用切片参数
t := max("", "foo", "bar") // t == "foo" （字符串类型）

```

**Clear Function**
**清空函数**

The clear function is a built-in function that takes an argument of type map, slice, or type parameter type. It is used to delete or zero out all the elements within the provided data structure.
clear 函数是一个内置函数，它接受类型为 map、slice 或类型参数。它用于删除或清空所提供的数据结构中的所有元素。

```
var a = [...]int{0, 1, 2, 3, 4, 5, 6, 7}
Expand All @@ -141,25 +140,25 @@ func main() {
}
```

## Improved Type Inference for Generic Functions
## 泛型函数的类型推断的改进

The type inference system for generic functions has received several improvements in Go 1.21. The Go specification now includes an expanded and clarified description of type inference, making it easier for developers to understand and utilize this powerful feature.
泛型函数的类型推断在 Go 1.21 中得到了多项改进。Go 说明中现在包含了对类型推断的扩充和清晰的描述，使开发人员更容易理解和利用这一强大的功能。

```
// Improved type inference for generic functions
// 泛型函数的类型推断的改进
```

```go
func genericFunc[T any](x T) {
// Function implementation
// 函数实现
}
value := 42
genericFunc(value) // Type inference automatically detects the type of value
genericFunc(value) // 类型推断自动检测值的类型
```

## Preview of Loop Variable Capture Improvement
## 循环变量捕获改进的预览功能

Go 1.21 introduces a preview feature aimed at addressing the common challenge of loop variable capture in Go programming. Developers can enable this feature in their code using an environment variable.
Go 1.21 引入了预览功能，旨在解决 Go 编程中循环变量捕获的常见挑战。开发人员可以通过使用环境变量 `GOEXPERIMENT=loopwar` 启用此功能。

```go
var out []*int
Expand All @@ -170,7 +169,7 @@ fmt.Println("Values:", *out[0], *out[1], *out[2])
fmt.Println("Addresses:", out[0], out[1], out[2])
```

`goroutine` Example that prints `1…10`
`goroutine` 打印 `1…10` 的例子

```go
for i := 1; i <= 10; i++ {
Expand All @@ -180,28 +179,29 @@ for i := 1; i <= 10; i++ {
}
```

## New Introduced Packages:
## 新引入的包

- 用于结构化日志记录的新 [log/slog包](https://pkg.go.dev/log/slog@master)
- 用于切片常见操作的新 [slices包](https://pkg.go.dev/slices@master)
- 字典常用操作的新 [map包](https://pkg.go.dev/maps@master)
- 用于比较有序值的新 [cmp包](https://pkg.go.dev/cmp@master)

- New [log/slog Package](https://pkg.go.dev/log/slog@master) for Structured Logging
- New [slices Package](https://pkg.go.dev/slices@master) for Common Operations on Slices
- New [maps Package](https://pkg.go.dev/maps@master) for Common Operations on Maps
- New [cmp Package](https://pkg.go.dev/cmp@master) for Comparing Ordered Values

## Improved Performance:
## 性能提升

Improved Performance with PGO:In addition to the performance improvements from enabling PGO, Go 1.21 brings additional enhancements to overall performance.
使用 PGO 改进性能：除了启用 PGO 带来的性能改进之外，Go 1.21 还对整体性能带来了额外的增强。

## New Experimental Port for WebAssembly System Interface (WASI):
## WebAssembly System Interface（WASI）的新实验端口：

Go 1.21 introduces an experimental port for the WebAssembly System Interface (WASI) — Preview 1, allowing developers to compile their Go code for the WebAssembly platform.
Go 1.21 引入了 WebAssembly System Interface (WASI) 的实验性端口 - Preview 1，这将允许开发人员为 WebAssembly 平台编译 Go 代码。

## Conclusion
## 总结

Go 1.21 offers enhancements in tooling, language features, standard library additions, and performance optimizations make Go an even more robust and efficient programming language for various use cases. With the availability of the Release Candidate, developers are encouraged to experiment, test, and provide feedback to help shape the final release slated for August 2023.
Go 1.21 在工具、语言功能、标准库添加和性能优化方面提供了增强，使 Go 成为适用于各种场景的更强大、更高效的编程语言。随着候选版本的推出，我们鼓励开发人员进行试验、测试并提供反馈，以帮助制定定于 2023 年 8 月发布的最终版本。

source: [https://go.dev/blog/go1.21rc#:~:text=Go%201.21%20adds%20an%20experimental,WASM%20host%3A%20go%3Awasmimport%20.](https://go.dev/blog/go1.21rc#:~:text=Go%201.21%20adds%20an%20experimental,WASM%20host%3A%20go%3Awasmimport%20.)
来源: [https://go.dev/blog/go1.21rc#:~:text=Go%201.21%20adds%20an%20experimental,WASM%20host%3A%20go%3Awasmimport%20.](https://go.dev/blog/go1.21rc#:~:text=Go%201.21%20adds%20an%20experimental,WASM%20host%3A%20go%3Awasmimport%20.)

Reference:
参考:

- [https://go.dev/blog/go1.21rc#:~:text=Go%201.21%20adds%20an%20experimental,WASM%20host%3A%20go%3Awasmimport%20.](https://go.dev/blog/go1.21rc#:~:text=Go%201.21%20adds%20an%20experimental,WASM%20host%3A%20go%3Awasmimport%20.)
- [https://go.dev/doc/pgo#:~:text=Profile%2Dguided%20optimization%20(PGO)%2C%20also%20known%20as%20feedback,information%20to%20make%20more%20informed](https://go.dev/doc/pgo#:~:text=Profile%2Dguided%20optimization%20(PGO)%2C%20also%20known%20as%20feedback,information%20to%20make%20more%20informed)
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