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[go/en] update for modern go (#4678)

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Sean Liao 2024-05-15 03:52:23 +01:00 committed by GitHub
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@ -32,11 +32,11 @@ Go comes with a good standard library and a sizeable community.
/* Multi-
line comment */
/* A build tag is a line comment starting with // +build
/* A build tag is a line comment starting with //go:build
and can be executed by go build -tags="foo bar" command.
Build tags are placed before the package clause near or at the top of the file
followed by a blank line or other line comments. */
// +build prod, dev, test
//go:build prod || dev || test
// A package clause starts every source file.
// main is a special name declaring an executable rather than a library.
@ -44,12 +44,13 @@ package main
// Import declaration declares library packages referenced in this file.
import (
"fmt" // A package in the Go standard library.
"io/ioutil" // Implements some I/O utility functions.
m "math" // Math library with local alias m.
"net/http" // Yes, a web server!
"os" // OS functions like working with the file system
"strconv" // String conversions.
"fmt" // A package in the Go standard library.
"io" // Implements some I/O utility functions.
m "math" // Math library with local alias m.
"net/http" // Yes, a web server!
_ "net/http/pprof" // Profiling library imported only for side effects
"os" // OS functions like working with the file system
"strconv" // String conversions.
)
// A function definition. Main is special. It is the entry point for the
@ -106,13 +107,13 @@ can include line breaks.` // Same string type.
n := byte('\n') // byte is an alias for uint8.
// Arrays have size fixed at compile time.
var a4 [4]int // An array of 4 ints, initialized to all 0.
var a4 [4]int // An array of 4 ints, initialized to all 0.
a5 := [...]int{3, 1, 5, 10, 100} // An array initialized with a fixed size of five
// elements, with values 3, 1, 5, 10, and 100.
// Arrays have value semantics.
a4_cpy := a4 // a4_cpy is a copy of a4, two separate instances.
a4_cpy[0] = 25 // Only a4_cpy is changed, a4 stays the same.
a4_cpy := a4 // a4_cpy is a copy of a4, two separate instances.
a4_cpy[0] = 25 // Only a4_cpy is changed, a4 stays the same.
fmt.Println(a4_cpy[0] == a4[0]) // false
// Slices have dynamic size. Arrays and slices each have advantages
@ -123,24 +124,24 @@ can include line breaks.` // Same string type.
bs := []byte("a slice") // Type conversion syntax.
// Slices (as well as maps and channels) have reference semantics.
s3_cpy := s3 // Both variables point to the same instance.
s3_cpy[0] = 0 // Which means both are updated.
fmt.Println(s3_cpy[0] == s3[0]) // true
s3_cpy := s3 // Both variables point to the same instance.
s3_cpy[0] = 0 // Which means both are updated.
fmt.Println(s3_cpy[0] == s3[0]) // true
// Because they are dynamic, slices can be appended to on-demand.
// To append elements to a slice, the built-in append() function is used.
// First argument is a slice to which we are appending. Commonly,
// the slice variable is updated in place, as in example below.
s := []int{1, 2, 3} // Result is a slice of length 3.
s = append(s, 4, 5, 6) // Added 3 elements. Slice now has length of 6.
fmt.Println(s) // Updated slice is now [1 2 3 4 5 6]
s := []int{1, 2, 3} // Result is a slice of length 3.
s = append(s, 4, 5, 6) // Added 3 elements. Slice now has length of 6.
fmt.Println(s) // Updated slice is now [1 2 3 4 5 6]
// To append another slice, instead of list of atomic elements we can
// pass a reference to a slice or a slice literal like this, with a
// trailing ellipsis, meaning take a slice and unpack its elements,
// appending them to slice s.
s = append(s, []int{7, 8, 9}...) // Second argument is a slice literal.
fmt.Println(s) // Updated slice is now [1 2 3 4 5 6 7 8 9]
fmt.Println(s) // Updated slice is now [1 2 3 4 5 6 7 8 9]
p, q := learnMemory() // Declares p, q to be type pointer to int.
fmt.Println(*p, *q) // * follows a pointer. This prints two ints.
@ -160,7 +161,7 @@ can include line breaks.` // Same string type.
file, _ := os.Create("output.txt")
fmt.Fprint(file, "This is how you write to a file, by the way")
file.Close()
// Output of course counts as using a variable.
fmt.Println(s, c, a4, s3, d2, m)
@ -179,7 +180,7 @@ func learnNamedReturns(x, y int) (z int) {
// Go is fully garbage collected. It has pointers but no pointer arithmetic.
// You can make a mistake with a nil pointer, but not by incrementing a pointer.
// Unlike in C/Cpp taking and returning an address of a local variable is also safe.
// Unlike in C/Cpp taking and returning an address of a local variable is also safe.
func learnMemory() (p, q *int) {
// Named return values p and q have type pointer to int.
p = new(int) // Built-in function new allocates memory.
@ -190,7 +191,7 @@ func learnMemory() (p, q *int) {
return &s[3], &r // & takes the address of an object.
}
// Use the aliased math library (see imports, above)
// Use the aliased math library (see imports, above)
func expensiveComputation() float64 {
return m.Exp(10)
}
@ -214,8 +215,8 @@ func learnFlowControl() {
case 42:
// Cases don't "fall through".
/*
There is a `fallthrough` keyword however, see:
https://github.com/golang/go/wiki/Switch#fall-through
There is a `fallthrough` keyword however, see:
https://github.com/golang/go/wiki/Switch#fall-through
*/
case 43:
// Unreached.
@ -355,7 +356,7 @@ func learnInterfaces() {
}
// Functions can have variadic parameters.
func learnVariadicParams(myStrings ...interface{}) {
func learnVariadicParams(myStrings ...any) { // any is an alias for interface{}
// Iterate each value of the variadic.
// The underscore here is ignoring the index argument of the array.
for _, param := range myStrings {
@ -428,7 +429,6 @@ func learnConcurrency() {
// A single function from package http starts a web server.
func learnWebProgramming() {
// First parameter of ListenAndServe is TCP address to listen to.
// Second parameter is an interface, specifically http.Handler.
go func() {
@ -449,7 +449,7 @@ func requestServer() {
resp, err := http.Get("http://localhost:8080")
fmt.Println(err)
defer resp.Body.Close()
body, err := ioutil.ReadAll(resp.Body)
body, err := io.ReadAll(resp.Body)
fmt.Printf("\nWebserver said: `%s`", string(body))
}
```
@ -457,20 +457,23 @@ func requestServer() {
## Further Reading
The root of all things Go is the [official Go web site](https://go.dev/).
There you can follow the tutorial, play interactively, and read lots.
There you can follow the [tutorial](https://go.dev/tour/), play interactively, and read lots.
Aside from a tour, [the docs](https://go.dev/doc/) contain information on
how to write clean and effective Go code, package and command docs, and release history.
The [Go language specification](https://go.dev/ref/spec) itself is highly recommended. It's easy to read
and amazingly short (as language definitions go these days.)
You can play around with the code on [Go playground](https://go.dev/play/p/tnWMjr16Mm). Try to change it and run it from your browser! Note that you can use [https://go.dev/play/](https://go.dev/play/) as a [REPL](https://en.wikipedia.org/wiki/Read-eval-print_loop) to test things and code in your browser, without even installing Go.
You can play around with the code on [Go playground](https://go.dev/play/p/Y96bRpJWzjr).
Try to change it and run it from your browser!
Note that you can use [https://go.dev/play/](https://go.dev/play/)
as a [REPL](https://en.wikipedia.org/wiki/Read-eval-print_loop) to test things and code in your browser, without even installing Go.
On the reading list for students of Go is the [source code to the standard
library](https://go.dev/src/). Comprehensively documented, it
demonstrates the best of readable and understandable Go, Go style, and Go
idioms. Or you can click on a function name in [the
documentation](https://go.dev/pkg/) and the source code comes up!
documentation](https://pkg.go.dev/std) and the source code comes up!
Another great resource to learn Go is [Go by example](https://gobyexample.com/).
@ -480,4 +483,6 @@ There are many excellent conference talks and video tutorials on Go available on
- [Golang University 201](https://www.youtube.com/playlist?list=PLEcwzBXTPUE_5m_JaMXmGEFgduH8EsuTs) steps it up a notch, explaining important techniques like testing, web services, and APIs
- [Golang University 301](https://www.youtube.com/playlist?list=PLEcwzBXTPUE8KvXRFmmfPEUmKoy9LfmAf) dives into more advanced topics like the Go scheduler, implementation of maps and channels, and optimisation techniques
Go Mobile adds support for mobile platforms (Android and iOS). You can write all-Go native mobile apps or write a library that contains bindings from a Go package, which can be invoked via Java (Android) and Objective-C (iOS). Check out the [Go Mobile page](https://github.com/golang/go/wiki/Mobile) for more information.
Go Mobile adds support for mobile platforms (Android and iOS).
You can write all-Go native mobile apps or write a library that contains bindings from a Go package,
which can be invoked via Java (Android) and Objective-C (iOS). Check out the [Go Mobile page](https://github.com/golang/go/wiki/Mobile) for more information.