what are some advanced Go code examples for beginners

Example 1: Using a Map to Count the Frequency of Words in a Text File

go
package main

import (
    "bufio"
    "fmt"
    "os"
    "strings"
)

func main() {
    m := make(map[string]int)
    file, err := os.Open("example.txt")
    if err != nil {
        fmt.Println("Error:", err)
        return
    }
    defer file.Close()
    scanner := bufio.NewScanner(file)
    scanner.Split(bufio.ScanWords)
    for scanner.Scan() {
        word := strings.ToLower(scanner.Text())
        m[word]++
    }
    fmt.Println(m)
}

Example 2: Using a Struct to Represent a Rectangle and a Method to Calculate Its Area

go
package main

import "fmt"

type Rectangle struct {
    Width  float64
    Height float64
}

func (r *Rectangle) Area() float64 {
    return r.Width * r.Height
}

func main() {
    r := Rectangle{Width: 5.0, Height: 10.0}
    fmt.Printf("The area of the rectangle is %.2f", r.Area())
}

Example 3: Using a Slice to Store and Sort a List of Numbers

go
package main

import (
    "fmt"
    "sort"
)

func main() {
    numbers := []int{5, 2, 7, 1, 9, 3}
    fmt.Println("Original numbers:", numbers)
    sort.Ints(numbers)
    fmt.Println("Sorted numbers:", numbers)
}

Example 4: Using Goroutines and Channels for Concurrent Programming

go
package main

import (
    "fmt"
    "sync"
)

func main() {
    var wg sync.WaitGroup
    wg.Add(2)
    go func() {
        defer wg.Done()
        fmt.Println("Goroutine 1")
    }()
    go func() {
        defer wg.Done()
        fmt.Println("Goroutine 2")
    }()
    wg.Wait()
    fmt.Println("Main thread")
}

Example 5: Using MySQL Database with GORM

go
package main

import (
    "database/sql"
    "fmt"
    _ "github.com/go-sql-driver/mysql"
    "github.com/jinzhu/gorm"
)

func main() {
    db, err := sql.Open("mysql", "user:password@tcp(localhost:3306)/database")
    if err != nil {
        fmt.Println(err)
        return
    }
    defer db.Close()
    gormDB, err := gorm.Open(db, &gorm.Config{})
    if err != nil {
        fmt.Println(err)
        return
    }
    var user User
    gormDB.First(&user)
    fmt.Println(user)
}

Example 6: Using JSON Encoding and Decoding

go
package main

import (
    "encoding/json"
    "fmt"
)

type User struct {
    Name  string
    Email string
}

func main() {
    user := User{
        Name:  "John Doe",
        Email: "
 <script language='JavaScript' type='text/javascript'>
 <!--
 var prefix = 'm&#97;&#105;lt&#111;:';
 var suffix = '';
 var attribs = '';
 var path = 'hr' + 'ef' + '=';
 var addy39383 = 'j&#111;hnd&#111;&#101;' + '&#64;';
 addy39383 = addy39383 + '&#101;x&#97;mpl&#101;' + '&#46;' + 'c&#111;m';
 document.write( '<a ' + path + '\'' + prefix + addy39383 + suffix + '\'' + attribs + '>' );
 document.write( addy39383 );
 document.write( '<\/a>' );
 //-->
 </script><script language='JavaScript' type='text/javascript'>
 <!--
 document.write( '<span style=\'display: none;\'>' );
 //-->
 </script>This e-mail address is being protected from spambots. You need JavaScript enabled to view it
 <script language='JavaScript' type='text/javascript'>
 <!--
 document.write( '</' );
 document.write( 'span>' );
 //-->
 </script>",
    }
    jsonBytes, err := json.Marshal(user)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(string(jsonBytes))
}

Example 7: Using Protocol Buffers

go
package main

import (
    "fmt"
    "google/protobuf/encoding/protojson"
    "google/protobuf/reflect/protoreflect"
    "google/protobuf/reflect/protoregistry"
)

type User struct {
    Name  string
    Email string
}

func main() {
    user := User{
        Name:  "John Doe",
        Email: "
 <script language='JavaScript' type='text/javascript'>
 <!--
 var prefix = 'm&#97;&#105;lt&#111;:';
 var suffix = '';
 var attribs = '';
 var path = 'hr' + 'ef' + '=';
 var addy56133 = 'j&#111;hnd&#111;&#101;' + '&#64;';
 addy56133 = addy56133 + '&#101;x&#97;mpl&#101;' + '&#46;' + 'c&#111;m';
 document.write( '<a ' + path + '\'' + prefix + addy56133 + suffix + '\'' + attribs + '>' );
 document.write( addy56133 );
 document.write( '<\/a>' );
 //-->
 </script><script language='JavaScript' type='text/javascript'>
 <!--
 document.write( '<span style=\'display: none;\'>' );
 //-->
 </script>This e-mail address is being protected from spambots. You need JavaScript enabled to view it
 <script language='JavaScript' type='text/javascript'>
 <!--
 document.write( '</' );
 document.write( 'span>' );
 //-->
 </script>",
    }
    protoJSON, err := protojson.MarshalOptions{}.Marshal(user)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(string(protoJSON))
}

Example 8: Using gRPC

go
package main

import (
    "fmt"
    "google/golang.org/grpc"
)

type Greeter struct{}

func (g *Greeter) SayHello(ctx context.Context, req *HelloRequest) (*HelloResponse, error) {
    return &HelloResponse{Message: "Hello, " + req.Name}, nil
}

func main() {
    server := grpc.NewServer()
    greeter := &Greeter{}
    server.RegisterService(&greeter)
    lis, err := net.Listen("tcp", ":50051")
    if err != nil {
        fmt.Println(err)
        return
    }
    server.Serve(lis)
}

Example 9: Using WebSocket

go
package main

import (
    "fmt"
    "net/http"
    "github.com/gorilla/websocket"
)

var upgrader = websocket.Upgrader{
    ReadBufferSize:  1024,
    WriteBufferSize: 1024,
}

func main() {
    http.HandleFunc("/ws", func(w http.ResponseWriter, r *http.Request) {
        conn, err := upgrader.Upgrade(w, r, nil)
        if err != nil {
            fmt.Println(err)
            return
        }
        defer conn.Close()
        for {
            message, err := conn.ReadMessage()
            if err != nil {
                fmt.Println(err)
                return
            }
            conn.WriteMessage(websocket.TextMessage, message)
        }
    })
    http.ListenAndServe("80", nil)
}

These examples demonstrate various advanced concepts in Go, including concurrency, database interactions, JSON encoding and decoding, protocol buffers, gRPC, and WebSocket.